So firsty up, you need to have equal denominators IN order to do this equation.
1/3 and 5/12..
3x4=12
So the rule when changing denominators, you multiply 4 intop, so it will become 4/12, and 5/12 + 4/12 = 8/12, and,
8/12 + 1/12= 9/12 and 9/12 simplified is 3/4..
So the answer is 3/4.
Hope this helped.