RegularPrice - 20%*RegularPrice = $69.74

RegularPrice(100% - 20%) = $69.74

RegularPrice = $69.74/(100%-20%) = $69.74/80% = $69.74/.80

RegularPrice = $87.175

It could have been either of $87.18 or $87.17.

Check

$87.17 * 20% = $17.43

$87.17 - $17.43 = $69.74

$87.18 * 20% = $17.44

$87.17 - $17.44 = $69.74

_____

Be careful here. The math bureaucrats who make up test questions will probably only count $87.18 as the correct answer. That answer shows that you know how to round properly to 2 decimal digits. The math bureaucrats don't take kindly to being told they are wrong, even when it can be demonstrated that there are other possibilities--as above.

RegularPrice(100% - 20%) = $69.74

RegularPrice = $69.74/(100%-20%) = $69.74/80% = $69.74/.80

RegularPrice = $87.175

It could have been either of $87.18 or $87.17.

Check

$87.17 * 20% = $17.43

$87.17 - $17.43 = $69.74

$87.18 * 20% = $17.44

$87.17 - $17.44 = $69.74

_____

Be careful here. The math bureaucrats who make up test questions will probably only count $87.18 as the correct answer. That answer shows that you know how to round properly to 2 decimal digits. The math bureaucrats don't take kindly to being told they are wrong, even when it can be demonstrated that there are other possibilities--as above.