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

p = x + y + z
p = 8cm + 5cm + 12cm = 25cm

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

7a + 2z = -3a - 7z + 5
7a = -3a - 7z + 5 - 2z
7a + 3a = -7z + 5 - 2z
10a = -9z + 5
a = \( \frac{-9z + 5}{10} \)
a = \( \frac{-9z}{10} \) + \( \frac{5}{10} \)
a = -\(\frac{9}{10}\)z + \(\frac{1}{2}\)

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.

-3x - 8 = \( \frac{x}{7} \)
7 x (-3x - 8) = x
(7 x -3x) + (7 x -8) = x
-21x - 56 = x
-21x - 56 - x = 0
-21x - x = 56
-22x = 56
x = \( \frac{56}{-22} \)
x = -2\(\frac{6}{11}\)

An equation is two expressions separated by an equal sign. The key to solving equations is to 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.

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.