Question

A number is twice another number if 15 is subtracted from both the number then the bigger number becomes thrice that of a small number find the number

Answer 1

let the number be x
and other number be 2x
$if \: \frac{x - 15}{2x - 15} = \frac{1}{3} \\ then \: cross \: multiply \\ 3(x - 15) = 1(2x - 15) \\ 3x - 45 = 2x - 15 \\ 3x - 2x = 45 - 15 \\ x = 30$
$the \: bigger \: no \: is \: 60 \\ the \: smaller \: no \: is \: 30$