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!