Area of a trapezium = [a+b]h2\; \frac{[a+b]h}{2}2[a+b]h
105 = [9+12]h2\; \frac{[9+12]h}{2}2[9+12]h → 105 x 2 =21h
h = 21021\; \frac{210}{21}21210 → 10cm
