A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

When solving an equation with two variables, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

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 4 x 1) + (2 x 1 x 3) + (2 x 4 x 3)
sa = (8) + (6) + (24)
sa = 38

To factor a quadratic expression, apply the FOIL method (First, Outside, Inside, Last) in reverse. First, find the two Last terms that will multiply to produce 20 as well and sum (Inside, Outside) to equal -9. For this problem, those two numbers are -5 and -4. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 9y + 20
y² + (-5 - 4)y + (-5 x -4)
(y - 5)(y - 4)

The volume of a cube is height x length x width:

v = h x l x w
v = 6 x 5 x 6
v = 180