Please help i have no idea how to do this

The area of a rectangle is length times width
l • w = 12 • 10 = 120 ft^2

the area of a triangle is 1/2 • b • h
b is base and h is height
1/2 • b • h = 1/2 • 6 • 7 = 21 ft^2

now subtract
120 - 21 = 99 ft^2 is the gray area