To find the percent of increase from one number to the next simply use this formula, 

$\displaystyle \small \frac{difference}{original} \times100$.

In this problem, our "difference" is just $\displaystyle \small 79-56 = 23$.

Next, we place that difference over our original, $\displaystyle \small \frac{23}{56}$, and then multiply against $\displaystyle \small 100$ in order to convert out answer to a percentage, resulting in about $\displaystyle \small 41.07\%$, $\displaystyle \small \approx41\%$. 

To find the original value, use the following relation.

$\displaystyle \frac{new-old}{old}*100=percentage$

We know the percentage, and we know the new value, so we can solve for the old value.

$\displaystyle \frac{21-old}{old}=.2$

$\displaystyle 21-old=.2old$

$\displaystyle 21=1.2old$

$\displaystyle old=\frac{21}{1.2}=17.5$

To find the percent change we use the formula 

$\displaystyle \small \frac{difference}{original} \times 100$.

In this problem, we are asked to find the percent increase from $\displaystyle \small 239$ to $\displaystyle \small 489$.

So our formula will look like this: 

$\displaystyle \small \frac{250}{239} \times 100 = 104.6$.

Thus, the percent increase from $\displaystyle \small 239$ to $\displaystyle \small 489$ is about $\displaystyle \small 104.6\%$. 

To find the percent increase from one number to the next, the first step is to find the difference between the two numbers given, $\displaystyle \small 589-389 = 200$.

The formula we use to solve this type of equation is: 

$\displaystyle \small \frac{difference}{original} \times 100.$.

Our original number here is $\displaystyle \small 389.$, so our formula: 

$\displaystyle \small \frac{200}{389}\times 100 \approx51.4\%.$ 

This means that from $\displaystyle \small 389$ to $\displaystyle \small 589$, we had to add about $\displaystyle \small 51.4\%$ of $\displaystyle \small 389$ to $\displaystyle \small 389$ to get $\displaystyle \small 589.$

To find the percent of increase from $\displaystyle \small 18982$ to $\displaystyle \small 21834$ we first must find the range between the numbers, 

$\displaystyle \small 21834-18982 = 2852$.

Then we use this formula to find the percent increase: 

$\displaystyle \small \frac{difference}{original}\times 100$.

For this data given, 

$\displaystyle \small \small \frac{2852}{18982} \times 100 \approx 15\%$. 

To find the percent change of the phone we will need to use the following formula.

$\displaystyle percent\:of \: change=\left | \frac{new-old}{old}\right |\ast100$

Applying our values 

$\displaystyle old=\$450$

$\displaystyle new=\$399$

to the percent change formula we find,

$\displaystyle percent\:of \: change=\left | \frac{399-450}{450}\right |\ast100=11.33\%$

To find the percent of increase from one number to the next, this formula is used: 

$\displaystyle \small \frac{difference}{original} \times 100$.

The numerator in this case would be 

$\displaystyle \small 15-12=3$.

So our formula would be 

$\displaystyle \small \frac{3}{12}\times 100 = 25\%$.

It is a $\displaystyle \small 25\%$ increase from $\displaystyle \small 12$ to $\displaystyle \small 15.$

To find the percent increase from $\displaystyle \small 100$ to $\displaystyle 124$, we first recognize that the formula needing to be used is 

$\displaystyle \small \frac{difference}{original}\times100$.

The difference here is, 

$\displaystyle \small 124-100=24$,

meaning our formula will look like this: 

$\displaystyle \small \frac{24}{100}\times 100 = 24\%$.

This, then, is our percent increase. 

For this type of problem we use this formula: 

$\displaystyle \small \frac{difference}{original} \times 100$.

"Difference" is simply the difference between the two numbers given, and "original" is the number that is stated usually after the word "from" , example: from $\displaystyle \small #$____ to ____.

In this problem our formula will be filled in as follows: 

$\displaystyle \small \frac{13-10}{10} \times 100 = \frac{3}{10}\times 100 =30\%$.

This our percent increase.

For this type of problem we use this formula: 

$\displaystyle \small \frac{difference}{original} \times 100$.

"Difference" is simply the difference between the two numbers given, and "original" is the number that is stated usually after the word "from" , example: from $\displaystyle \small #$____ to ____.

In this problem our formula will be filled in as follows: 

$\displaystyle \small \small \frac{35-26}{26} \times 100 = \frac{9}{26}\times 100 \approx35\%$.

This our percent increase.