If 36 is 80% ( a piece) of a number. that means the number must be higher than 36
Changing the English to math:
36 = 80% x n (n being the number)
36= .8n (changed the percent to a decimal by moving it back two places
36 = .8n
.8 .8 I divided both sides by .8 - when you divide a number by a decimal (less than one) the number will become larger.
The answer is 45