Add two fractions together.
Both fractions are put over a common denominator, then the numerators are added.
Sum: a/b + c/d = (a×d + c×b) ÷ (b×d)
Why do I need a common denominator to add fractions?
The bottom number of a fraction shows how big each piece is. You cannot add halves and thirds directly, until both are changed to the same size of piece.