After a 20% discount, Eduardo paid $140 for a skateboard. What was the price before the discount? How do you know your answer is correct?

$175

Step-by-step explanation:

If after a 20% discount, it cost $140, the $140 is only 80% of the cost.

So divide 140 by 4 then multiply the answer by 5 to get it back to 100%

140/4=35

35x5=175

you didn't post any answer choices, so its not 100% clear what your teacher is looking for

however, log(15/7) is equivalent to log(15) - log(7)

i'm using the rule log(x/y) = log(x) - log(y)