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

a = l x w
a = a x b
a = 5 x 7
a = 35

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, isolate the variable for which you are solving (b) on one side of the equation and put everything else on the other side.

-7b + 10x = 4b - 9x - 9
-7b = 4b - 9x - 9 - 10x
-7b - 4b = -9x - 9 - 10x
-11b = -19x - 9
b = \( \frac{-19x - 9}{-11} \)
b = \( \frac{-19x}{-11} \) + \( \frac{-9}{-11} \)
b = 1\(\frac{8}{11}\)x + \(\frac{9}{11}\)

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

c² - 5c + 4 = 0
(c - 1)(c - 4) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (c - 1) or (c - 4) must equal zero:

If (c - 1) = 0, c must equal 1
If (c - 4) = 0, c must equal 4

So the solution is that c = 1 or 4

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 2 x 4) + (2 x 4 x 2) + (2 x 2 x 2)
sa = (16) + (16) + (8)
sa = 40