How do I get 56?

Have u learnt algebra? If so, then use algebra to solve this qn?

Case 1 : If Kim gives away 21 stickers,

Ratio of their stickers is 3 : 4
So total units = 3 + 4 = 7

Case 2 : If Stef gives away 21 stickers,

Ratio of their stickers is 9 : 5
So total units = 9 + 5 = 14

Notice that in both cases, the total number of stickers decreases by 21. So their total remaining stickers is the same for both cases. So the number of units should be the same as well.

Make the number of units remaining in case 1 the same as case 2.

7 units x 2 = 14 units

So 3 : 4 → 6 : 8

Compare 6 : 8 (case 1) and 9 : 5 (case 2)

From this you can infer that Kim had 9 units at first and Stef had 8 units at first.

In both cases, one of them gave away 3 unit of stickers, which equals 21 stickers.

So 3 units = 21 stickers
1 unit = 21 ÷ 3 = 7 stickers


Stef had 8 units at first.

8 units = 8 x 7 stickers = 56 stickers

So Stef had 56 stickers at first.