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

a = l x w
a = a x b
a = 8 x 7
a = 56

A rectangle is a parallelogram containing four right angles. Opposite sides (a = c, b = d) are equal and the perimeter is the sum of the lengths of all sides (a + b + c + d) or, comonly, 2 x length x width. The area of a rectangle is length x width. A square is a rectangle with four equal length sides. The perimeter of a square is 4 x length of one side (4s) and the area is the length of one side squared (s²).

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.)

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

c - z = -6c + 8z - 1
c = -6c + 8z - 1 + z
c + 6c = 8z - 1 + z
7c = 9z - 1
c = \( \frac{9z - 1}{7} \)
c = \( \frac{9z}{7} \) + \( \frac{-1}{7} \)
c = 1\(\frac{2}{7}\)z - \(\frac{1}{7}\)

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.