Question

4 is 80% of what number?

Answer 1

Your equation would be 4=80%x. Let X represent the number you are looking for. 
First, you must change 80% in to a decimal because you cannot multiply a percent. 4=8x
Then, divide 4 by 8 to solve X. 
Your answer is .5. 
To check if your answer is correct, plug in .5 into the equation. 4=8×.5.

Answer 2

4 is 80% of 5, because 1 is worth 20%