Pies given to relatives = 1/5 = 3/15
Pies left = 2/3 = 10/15
Total pies = 15/15

So pies given away = 15/15 - 10/15 = 5/15

So pies given to friends = 5/15 - 3/15
= 2/15

2/15 = 30pies

Pies packed into the 18 boxes are those pies left over = 10/15

10/15 = 2/15 x 5 = 30 pies x 5 = 150 pies


ii)

Assume all boxes contained 12 pies first.

12 pies x 18 boxes = 216 pies

216 pies - 150 pies = 66 pies

This means we have over counted by 66 pies.

Since 12 - 6 = 6

By assuming that a 6-pie box was a 12-pie box instead, we have over counted by 6 pies per box.

66 ÷ 6 = 11 boxes

So this means 11 boxes were assumed to be 12-pie boxes. And this also tells you that actually there are 11 6-pie boxes only.