If $5$ mugs cost $£3.50$ and $8$ pens cost $£6.80$ how much change do I get from $£10$ if I buy $7$ mugs and $5$ pens? You MUST show your working. 
Overseas Competition->Knowledge Point->Calculation Modules->Decimals->Addition and Subtraction of Decimals Overseas Competition->Knowledge Point->Calculation Modules->Decimals->Multiplication and Division of Decimals Overseas Competition->Knowledge Point->Word Problem Modules->Word Problems in Economics->Money Calculation