Adding, you have to get the LCD first for the denominators. For example 1/2 + 1/3 the LCD is 6 so therefor you write 6 as the denominator. Then 6 divided by 2 = 3 so the first number would be 3/6 right now. Do the same process for the secon number. The number sentence should be 3/6 + 2/6 then copy the denominator then add the numinators.