In a basket, there were balls of three different sizes: large, medium and small. 2/3 of the balls were large, 1/5 of the balls were medium and the rest were small. There were 128 more large balls than small balls. How many small balls were there?

Answer 1

2/3 + 1/5 = 10/15 + 3/15 = 13/15
so
2/15 are small
(10/15 - 2/15) total number = 128
8 * total = 15 * 128
so total = 15 *16
so
small =2/15 * (15 * 16) = 32