You can solve this problem using a proportion.  

$\displaystyle \frac{1}{0.75}=\frac{12}{x}$

To solve for x, cross multiply.

$\displaystyle 1\times x=12\times.75$

$\displaystyle x=9.00$

9 dollars

You can use a proportion to solve this problem.  

$\displaystyle \frac{2}{50}=\frac{x}{200}$

Cross multiply to solve for x.  

$\displaystyle 50\times x=200\times2$

$\displaystyle 50x =400$

$\displaystyle 400\div50 = 8$

To Solve:

Multiply the $\displaystyle \$2.00$ Lola receives by the $\displaystyle 13.5$ hours Phil worked:

$\displaystyle \small $2.00 \cdot 13.5=27$

Phil will give Lola $\displaystyle \$27.00$ if he works $\displaystyle 13.5$ hours.

If the ratio of boys to girls in a classroom is $\displaystyle 11:12$, that means that there are $\displaystyle 11$ boys for every $\displaystyle 12$ girls. Thus, when there are $\displaystyle 23$ students in a classroom, the breakdown will be $\displaystyle 11$ boys and $\displaystyle 12$ girls. If there are $\displaystyle 46$ students in a classroom, the breakdown will be $\displaystyle 22$ boys and $\displaystyle 24$ girls, which translates to a ratio of $\displaystyle 22:24$, or $\displaystyle 11:12$. 

Thus, if there are $\displaystyle 46$ students, $\displaystyle 22$ will be boys. 

If $\displaystyle 490$ disagreed with the plan, that means the rest agreed.  

So to find that value, you must do the total minus the no's

$\displaystyle 500-490=10$.  

To find the proportion you must divide the part by the whole giving us an answer of $\displaystyle 0.02$ 

$\displaystyle 10/500=0.02$.

Since Mike does twice the work that Joe does, his part of the ratio must be double the value of Joe's.  The only ratio given that has that is $\displaystyle 2:1$.

If $\displaystyle \frac{A}{9} = \frac{B }{11}$, then:

The ratio of the numerators is equivalent to that of the denominators, in the same order. Hence,

$\displaystyle \frac{A}{B} = \frac{9} {11}$ and $\displaystyle \frac{9} {A}= \frac{11}{B }$ are true.

The reciprocals of the ratios are equivalent, so

$\displaystyle \frac {9}{A}= \frac{11}{B }$

However, it does not hold that 

$\displaystyle \frac{A}{11} = \frac{B }{9}$.

This can be seen as follows:

$\displaystyle \frac{A}{9} = \frac{B }{11}$

$\displaystyle \frac{A}{9} \cdot \frac{9}{11}= \frac{B }{11}\cdot \frac{9}{11}$

$\displaystyle \frac{A}{11}= \frac{9B }{121} \ne \frac{B}{9}$.

By a proportion property, if $\displaystyle \frac{A}{B} = \frac{C}{D}$, it follows that $\displaystyle \frac{A+B}{B} = \frac{C+ D}{D}$.

Setting $\displaystyle C= 3 , D = 4$, 

if $\displaystyle \frac{A}{B} = \frac{3}{4}$, then $\displaystyle \frac{A +B}{B} = \frac{3+4}{4} = \frac{7}{4}$.

The cross-products (the product of a numerator and the other denominator) of a proportion are equal, so, if

$\displaystyle \frac{A}{B} = \frac{5}{7}$, then

$\displaystyle 7 A = 5B$.

To solve:

Divide the total amount of Alice's allowance ($2.40) by the price for each snack ($ .60)

$\displaystyle 2.40\div 0.60=4$

Alice would be able to buy 4 snacks.