Kasim and Neil have 39 stickers between them; Neil and Carla have 44 stickers and the children have a total of 65 stickers.
How many stickers does Kasim have?
How many stickers does Carla have?
How many stickers do Carla and Kassim have between them?
From the first two statements we know Carla must have 5 stickers more than Kasim
So Kasim + Neil + (Kasim + 5 ie Carla) = 65
and Kasim + Neil is 39 so Kasim has 21
If Kasim has 21 then Neil has 18 (to get 39 between them) so Carla has 26 (5 more than K)
Writing it down is more complicated than doing it but hope you can follow