The area of a parallelogram is equal to its length x width:

a = l x w
a = a x b
a = 5 x 9
a = 45

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 5 x 4) + (2 x 4 x 8) + (2 x 5 x 8)
sa = (40) + (64) + (80)
sa = 184

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

5c + 5 = \( \frac{c}{-6} \)
-6 x (5c + 5) = c
(-6 x 5c) + (-6 x 5) = c
-30c - 30 = c
-30c - 30 - c = 0
-30c - c = 30
-31c = 30
c = \( \frac{30}{-31} \)
c = -\(\frac{30}{31}\)

A trapezoid is a quadrilateral with one set of parallel sides.