When he reached 13, Donnie's dad increased his weekly pocket-money by 25%. Donnie's pocket-money then went up to £15. How much did Donnie get per week when he was only 12?

Donnie's pocket money increased by 25% = 1/4

So you divide 15 by 4 = 3.75 which was his increased money

Then you minus 15.00 by 3.75 = 11.25

So Donnie got £11.25 every week when he was only 12.