I asked this already, but can somebody provide an answer with an explanation?

Answer:
Step-by-step explanation:
Area of triangles
Area of trapezoid
Since the area of trapezoid is same as the sum of the areas of the triangles, we have:
Concepts:
Answer: 41 cm²
Triangle lengths:
A(ABN) = 1/2b₁h
A(CDM)= 1/2b₂h
Trapezoid length:
A(ABCD) = 1/2(b₁ + b₂)h
A = 23 + 18 = 41 cm²