The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 12cm + 7cm + 9cm = 28cm

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).

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.

4z - 8 = \( \frac{z}{-5} \)
-5 x (4z - 8) = z
(-5 x 4z) + (-5 x -8) = z
-20z + 40 = z
-20z + 40 - z = 0
-20z - z = -40
-21z = -40
z = \( \frac{-40}{-21} \)
z = 1\(\frac{19}{21}\)

To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses:

(y + 1)(y + 3)
(y x y) + (y x 3) + (1 x y) + (1 x 3)
y² + 3y + y + 3
y² + 4y + 3

An isosceles triangle has two sides of equal length. An equilateral triangle has three sides of equal length. In a right triangle, two sides meet at a right angle.