I found the complete problem.
If Alice divides it into two trapezoids, the area formula would be: A = [(a+b) / 2] * h
Trapezoid 1
A = [(7.5 + 15)/2 * 5
A = (22.5/2) * 5
A = 11.25 * 5
A = 56.25 sq. ft
Trapezoid 2
A = [(5 + 10)/2 * 7.5
A = (15/2) * 7.5
A = 7.5 * 7.5
A = 56.25 sq. ft
Total area = 56.25 + 56.25 = 112.50 sq. ft.
If Alice divides it into two trapezoids, the area formula would be: A = [(a+b) / 2] * h
Trapezoid 1
A = [(7.5 + 15)/2 * 5
A = (22.5/2) * 5
A = 11.25 * 5
A = 56.25 sq. ft
Trapezoid 2
A = [(5 + 10)/2 * 7.5
A = (15/2) * 7.5
A = 7.5 * 7.5
A = 56.25 sq. ft
Total area = 56.25 + 56.25 = 112.50 sq. ft.