Question

a number consists of a two digit of which ten's digit exceeds the unit digit by 7 the number itself is equal to 10 times the sum of the digits. Find the number.

Answer 1

let tens digit be x
& units digit be y
x-y=7......................1
10x+y=10(x+y)
10x+y=10x+10y
9y=0
y=0
plug value of y in equation 1
x-y=7
x=7
the number is 7