Get the LCD (Least Common Denominator) of the Denominators then divide the new denominator (which is the LCD) to the numerator and multiply the quotient to the numerator. If the numbers can be simplified then do so.
Example:
3/6 + 5/10=
simplified form
3/6 +1/2= (LCD is 6) 3/6+ 3/6 = 6/6= 1
