To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

3a⁴ - 8a⁴ = -5a⁴

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.

2z + 5 = \( \frac{z}{9} \)
9 x (2z + 5) = z
(9 x 2z) + (9 x 5) = z
18z + 45 = z
18z + 45 - z = 0
18z - z = -45
17z = -45
z = \( \frac{-45}{17} \)
z = -2\(\frac{11}{17}\)

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.

8y - 8 = -5 + 4y
8y = -5 + 4y + 8
8y - 4y = -5 + 8
4y = 3
y = \( \frac{3}{4} \)
y = \(\frac{3}{4}\)

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 5 x 4) + (2 x 4 x 9) + (2 x 5 x 9)
sa = (40) + (72) + (90)
sa = 202

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.

5a + 8x = 9a - 5x - 8
5a = 9a - 5x - 8 - 8x
5a - 9a = -5x - 8 - 8x
-4a = -13x - 8
a = \( \frac{-13x - 8}{-4} \)
a = \( \frac{-13x}{-4} \) + \( \frac{-8}{-4} \)
a = 3\(\frac{1}{4}\)x + 2