Question

a number consists of two digits of which tens 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 70