Answer:
42ft^2
Start by splitting the "trapezoid" into two shapes ; triangle and square.
The triangle is a right triangle, so we can use the Pythagorean theorem to find its bottom side so we can find the unknown length of the square. This will also tell us the base of the triangle.
3^2 + b^2 = 5^2
b = 4
This means the square has the dimensions of 9ft by 4ft.
Multiply 9(4) for the area of the square --> A = b(h) = 9(4) = 36ft^2
Now for the triangle,
A= 1/2(b)(h)
base is 4, height is 3 thus:
A=1/2(4)(3) --> 12(1/2) = 6ft^2
Add the area of the triangle and square for the total area:
36ft^2 + 6ft^2 = 42ft^2