Abike is on sale for $170. this is 80% of the regular price. find the regular price

170-80%=136
i like it is $136 is the regular price
 you can also try to add them

You need to do proportions.
For this, I am going to set the numerator to only having prices and the denominator to only have the percentages.

170/80 = x/100,
where x is the regular price of the shirt, and the 100 is there because the regular price is technically 100% of the price.

So then we do cross multiplication and solve for x.
170(100) = 80x
17000= 80x
212.5 = x

So the bike's regular price is $212.50