90 ft² (option B)
Step-by-step explanation:
The diagram is a trapezoid:
The area of a trapezoid = 1/2 (base 1 + base 2) × height
base 1 = 8ft
base 2 = 12 ft
height = 9 ft
Area = 1/2 (8 + 12) × 9
Area = 1/2 (20) × 9 = 10 × 9
Area of the trapezoid = 90 ft² (option B)