You notice that we have in this figure 1 trapezoid, 1 rectangle & 1 right triangle.
Their respective area are as follow:
trapezoid = (B+b)xH/2==> B=6ft, b=3ft (side of rectangle) & H=11-7 =4
Area trapezoid =18 ft²
Rectangle = L x W =3x7 =21 ft²
Right Triangle = 2x3/2 = 3ft²
TOTAL AREA =18+21+2 =41 ft²