Question

When you use a coupon for 15% off the original price of a headset, you pay $27. What is the original price of the headset?

Answer 1

Let x represent the orig. price.  Then (100-15)% of x produces the sale price.  It is 0.85x = $27, so that

x = $31.76.

Check:  What is 15% off $31.76?  $4.76.

What is   $31.76 = $4.76?  $27.  This is correct.