Question

A two digit number is seven times the sum of its digits. the tens digit is 3 more than the units digit. what is the number

Answer 1

let x = the tenth digit and y the unit digit

is seven times the sum of its digits. 7( x+y) = 10 x +y
7x + 7 y = 10x + y
3x = 6y x= 6y / 3 = 2y x= 2y

we have that the tens digit is 3 more than the units digit so
x = 3 + y
we replace it in the first equation x= 2y
3+ y = 2y
y=3

and x= 6
so the number is 63