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

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