To solve this equation, 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.)

3a(a - x)
3(3)(3 + 6)
3(3)(9)
(9)(9)
81

The coordinate grid is composed of a horizontal x-axis and a vertical y-axis. The center of the grid, where the x-axis and y-axis meet, is called the origin.

A line segment is a portion of a line with a measurable length. The midpoint of a line segment is the point exactly halfway between the endpoints. The midpoint bisects (cuts in half) the line segment.

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 -7 as well and sum (Inside, Outside) to equal 6. For this problem, those two numbers are -1 and 7. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 6y - 7
y² + (-1 + 7)y + (-1 x 7)
(y - 1)(y + 7)

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

a = l x w
a = a x b
a = 8 x 1
a = 8