You have to find the most common denominator which for 1/2 and 1/8 is 8 and then you would do 1/2 1*3 and 2*4 to get 4/8 add them together for 5/8 then would would either add 24/8 to equal the 3 or you would leave the three by itself (depends on what your teacher says for simplification)
As for defining simplification it is solving the problem best you can with the information you are given.
