Question

50% of what number is 30

Answer 1

30 * 0.5 = ?

Answer 2

Think of it this way:

30 is half of what number?

You should be able to do that "in your head"

Answer 3

let the number be x then,
50% of x = 30
(50/100)* x = 30
0.5 x = 30
x = 30/0.5
x = 60

50% of 60 is 30