You know the area of a trapezoid is given by the formula
A = (1/2)(b₁+b₂)h
Solving for h, you get
h = 2A/(b₁+b₂)
The area in both cases is 42 cm², so the height will be given by
h = (2*42 cm²)/(b₁+b₂)
15. h = (84 cm²)/(5 cm + 7.5 cm) ≈ 6.7 cm
16. h = (84 cm²)/(5.7 cm + 10 cm) ≈ 5.4 cm
