Explanation:
A
this is the combination of a 4×6 rectangle and a 2×2 square. nothing is excluded.
so, the area is
(6-2)×6 + 2×2 = 4×6 + 4 = 24 + 4 = 28 cm²
B
this is the area of the large 8×5 rectangle minus the area of the small 2×3 rectangle.
so the area is
8×5 - 3×2 = 40 - 6 = 34 cm²
C
Basically the same thing as for B. large rectangle minus smaller rectangle.
so, the area is
15×10 - 9×6 = 150 - 54 = 96 cm²
D
the area of a triangle is
baseline × height / 2
or baseline here is 2×8, and the height is 5
so we get the area
2×8 × 5 / 2 = 8×5 = 40 cm²