Answer:
Area of a triangle=1/2×base x height
Let y represent the height
50cm²=1/2×20cm×y
50cm²=10cm×y
50cm²/10cm=10cm×y/10cm
5cm=y
therefore the height of the triangle is 5cm
Area of a trapezoid=1/2×a+b×height
let h represent the height
42cm²=(1/2×14cm+7cm)×h
42cm²=1/2×21cm×h
42cm²=21cm×h/2
42cm²×2=21cm×h(cross multiply)
84cm²=21cmh
84cm²/21cm=21cmh/21cm
4cm=h
Therefore the height is 4cm
