Find all values of X that solve the equation

I think Jane's friend said the original price was $48 since 20% of 40 is 8. Then he/she added 8 to 40 to get 48.

Jane's friend is incorrect.

Jane paid 80% of the original price, which is 0.8 in decimal form. We can write an equation to help us find the original price (where p is the original price)

0.8p=40
 
0.8     0.8
p=50

The original price was $50