Question

Twenty-one is 25% of

Answer 1

X * 25/100 = 21

x = 21 * 100/25 = 84

Answer 2

Let, that number = x
It would be: x * 25% = 21
x * 0.25 = 21
x = 21 / 0.25
x = 84

In short, Your Answer would be 84

Hope this helps!