Question

a two digit number is seven times the sum of its digit .if the difference between two digits is two.find the number

Answer 1

let two digit number be 10A+B,

then

10A+B=7(A+B),

10A+B=7A+7B,

10A-7A+B-7B=0,

then
3A-6B=0,

then

A-2B=0,...........eq(1),

also
A-B=2,..................eq(2),

on solving these two equations, we have

A=4,

B=2,

therefore
two digit number =10×4+2=42✓✓✓✓