Question 182981
Since "percent" is defined as:
"part"/"whole" * 100 = "percent"
.
In your problem:
42 is 40% of what number? 
.
They give you:
"part" = 42
"percent" = 40
.
What you are missing is "whole" -- which is "the number" you are looking for.
.
Assign a variable to things you don't know:
Let N = "the number"
then because:
"part"/"whole" * 100 = "percent"
we then have:
(42/N)100 = 40  (This is your equation)