a) We need Area of Trapezium ABCD
So AB = 8, BC = 14, and AD = 20
We need the Area of the box made if a horizontal line went left from C, plus the triangle that line leaves above the box. Since the line would cut the AD off at 14, there is 20-14=6 left over forming the left side of the triangle. The bottom (base) of the triangle is 8 just like the bottom of the box.
So area of the box = L×W = 14×8 = 112
And area of the triangle = 1/2×B×H
= 1/2×8×6 = 24 --> so 112 + 24 = 136
b) wants to know the length of CD, which turns out to be the hypotenuse of the right triangle we made to solve the last problem
Use Pythagorean Theorem for right triangles, where c = hypotenuse
c^2 = a^2 + b^2 --> c^2 = 6^2 + 8^2 --> c^2 = 36 + 64 = 100
So square root (c^2) = square root (100) --> c = 10