The sum of the digits of a two number is 6. The number with the digits interchanged is 3 times the tens digit of the original number. Find the original number.
let the tens digit be x
let the unit digit by y
x+y=6 ---> y = 6-x
original number = 10x + y
number reversed = 10y + x
10y + x = 3x
10y = 2x
x = 5y
then y = 6 - 5y
6y=6
y=1
and x=5(1) = 5
the original number is 51