Answer:
20
Explanation:
First, the rectangle is 10 by 5, so an easy 50. Then we have the triangle. The base is 5, and since the whole height is 18 and the rectangle's is 10, 18-10=8. The formula for a triangle is 1/2(b)h, so:
1/2*5=2.5
2.5*8=20 cm
Hope this helps!