72 is the result of x-20% Help please--the way that I thought of solving this is not what the book says the answer is​

The original cost was $90.

Step-by-step explanation:

"Judy bought a coat at the office of $72, which is 20% off the original price. what was the original cost of the coat?"

Your equation contains an error that will lead to an incorrect answer.

This is the correct way to write the equation.

We don't know the original price, so we let x = the original price.

The discount was 20% off the original price, so the discount is 20% of x.

20% of x is the same as 20% * x = 0.2x. The discount is 0.2x. We now subtract the discount from the original price.

x - 0.2x

She paid the discounted price of x - 0.2x. We are told that amount is $72, so we let our expression of the discounted price equal the discounted price we are told she paid.

x - 0.2x = 72

Now we solve for x, the original price.

x - 0.2x = 72

Combine like terms on the left side.

0.8x = 72

Divide both sides by 0.8

0.8x/0.8 = 72/0.8

x = 90

The original cost was $90.

P.S.

You must be careful when writing the equation. What you wrote was

x - 20%

on the left side. Notice that 20% is simply equal to 0.2; it is not 20% of the original price. By writing

x - 20% = 72

you are in fact writing

x - 0.2 = 72

meaning that the discount was $0.20

A discount of 20% on $90 is really $18, not $0.20.

There is a big difference there.

If you have any questions, just ask in the comments.

step-by-step explanation: