Question

57 is 13.5 of what number

Answer 1

you mean 13.5 percent?

Answer 2

let x be the number.
13.5(x)=57.
x=4.222222222222

Answer 3

if it's 13.5%

57 = 0.135*x and solve for x

if it's 13.5 times a number

57 = 13.5*x and solve for x