It is an even, two digit number. The difference between the digits is three. The ones digit is twice the 10 digit

Answer 1

If you're not required to solve this with algebra, don't. It's much easier with logic and eliminating impossibilities, as follows.

Let's call our two-digit number ab, with a being the tens digit and b the units (ones) digit.

If the ones digit is double the tens, then the ones digit can only be 2, 4, 6, or 8, which means the tens digit can only be 1, 2, 3, or 4. That narrows is down quite a bit. The fact that the number is even is already taken care of, since all the ones possibilities are even. So which pair could give us a-b=3 or b-a=3 ? Only 36.