I would first solve how long it takes for 1 tyres to make life easier. Just solve 56 divided by 4, which means that Liam takes 14 minutes to put one tyres into the van. For part a, I don't quite understand the 3 vans part, but you know he 's putting 12 tyres into a van, so multiply 12 by 14 to get 156. Part B gives you time instead of tyres. Solve it practically the same... 42 divided 14 is 3, so he fits 3 tyres in 42 minutes,