Answer:
8 + 6 = 14
14 x 4 = 56
56 x 1/2(basically just dividing by 2) = 28 mm2
Formula of area of a trapezoid:
B1(base 1) + B2(base 2) x H(height) x 1/2(basically just dividing by 2)
In this case, 8 is your base your other base is 6 and your height is 4.