Area of a Trapezium - Finding missing lengths

I wanted something a little more challenging on the topic of Trapezia that still gave my students plenty of practice calculating areas, so I designed these questions. In each question, students are given a pair of trapezia and are told how their areas are linked (one is a multiple of the other). Students have to determine the area of one trapezium, use that to determine the area of the other one, and then finally use that to determine a missing value.

Sheets I and II are very similar, but sheet III is a bit more challenging. Solutions are provided.