There are 30 stickers in Container C and 15 stickers in Container D.
Some stickers are transferred from Container C to Container D.
Container D has 15 more stickers than Container C.
How many stickers are transferred from Container C to Container D?

	Container C	Container D
Before	30	15
Change	- ?	+ ?
After	1 u	1 u + 15

Total number of stickers
= 30 + 15
= 45

In the end
Total number of stickers = 1 u + 1 u + 15 = 2 u + 15

The total number of stickers at first and in the end remains unchanged.

2 u + 15 = 45
2 u = 45 - 15 = 30

1 u = 30 ÷ 2 = 15

Number of stickers that are transferred from Container C to Container D
= Number of stickers in Container C at first - Number of stickers in Container C in the end
= 30 - 15
= 15

Answer(s): 15