Question

The units digit of a two digit number is 3 and seven times the sum of the digit is the number itself. Find the number?

Answer 1

10Y+X WHERE X=3,
7(Y+X)=10Y+X
BY SOLVING THIS WE GET Y=6
THE NUMBER = 63

Answer 2

let the number be xy
here unit digit is y
ten's digit is x
according to question y=3
$10x + y = 7(x + y) \\ put \: the \: value \: of \: y \: in \: the \: equation \\ 10x + 3 = 7(x + 3) \\ 10x + 3 = 7x + 21 \\ 10x - 7x = 21 - 3 \\ 3x = 18 \\ x = \frac{18}{3} \\ x = 6$
so the number is 63