##### Math makes my head hurt.

,When adding or subtracting fractions or mixed numbers, we must first find equivalent fractions that have the **same denominators**, since the parts are not the same size. So we can re-write five and one third as five and five fifthteenths and we can also rewrite two and two fifths as two and 6 fifthteenths. So the two fractions now have the same denominator. Hope this helps!