We can use ratios and proportions to solve this problem. Percentages can be written as ratios. The word “percent” means for every hundred. In the problem, we are told that  of the cars are red. In other words, for every hundred cars  of them are red. We can write the following ratio:

Reduce.

We know that there are  cars in the parking lot. We can write the following ratio by substituting the variable  for the number of red cars:

Now, we can create a proportion using our two ratios.

Cross multiply and solve for .

Simplify.

Divide both sides of the equation by .

Solve.

There are  red cars in the parking lot.

We can use ratios and proportions to solve this problem. Percentages can be written as ratios. The word “percent” means for every hundred. In the problem, we are told that  of the cars are red. In other words, for every hundred cars  of them are red. We can write the following ratio:

Reduce.

We know that there are  cars in the parking lot. We can write the following ratio by substituting the variable  for the number of red cars:

Now, we can create a proportion using our two ratios.

Cross multiply and solve for .

Simplify.

Divide both sides of the equation by .

Solve.

There are  red cars in the parking lot.

Each statement can be written as a proportion, and solved for its variable by cross-multiplying. In each case, we replace as follows:

(a) The percent is 40, the part is 200, and the whole is :

(b) The percent is 70, the part is 350, and the whole is :

Paying for something at 20% discount is the same as paying for it at 80% of the price. 

If the boom box costs $172.80 before a 20% discount, then afterward, it costs 80% of this, or

Therefore, the original price must have been greater than $172.80.

No clue is given as to how much Chet paid for the device - neither the price paid for the player nor the amount of money Chet gave the clerk is given here.

60% of 3,000 is equal to .

40% of an unknown number  can be written as . Set these equal  and solve for :

Since the game was 20% off, that means the game's value is currently 80% of the original price.

In order to figure out what the original price of the game was, you must set up a proportion:

The proportion is set up this way because the $32 Claude paid is equal to 80% of the price of the game, not 100%. The x stands for the unknown original price of the game. Next, cross multiply. The bottom number of each fraction should be multiplied by the top number. 

The above will be your result. You then must solve for x. To do this, divide by 80 on each side of the equation.

The value of x is your answer.

Remember that for percentages, the key to setting up the problem is intelligent translation. The word "is" becomes , "of" signals multiplication, "what" (and equivalent words) signal a variable ().

Therefore, we can translate:

 is % of what number?

As...

To solve, divide both sides by :

Rounded, this is:

Remember that for percentages, the key to setting up the problem is intelligent translation. The word "is" becomes , "of" signals multiplication, "what" (and equivalent words) signal a variable ().

Therefore, we can translate:

 is % of what number?

As . . .

To solve, divide both sides by :

Rounded, this is:

Remember that for percentages, the key to setting up the problem is intelligent translation. The word "is" becomes , "of" signals multiplication, "what" (and equivalent words) signal a variable ().

Therefore, we can translate:

 is % of what number?

As...

To solve, divide both sides by :

Rounded, this is: