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.

7a³ + 2a³ = 9a³

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.

-6x - 6 = \( \frac{x}{3} \)
3 x (-6x - 6) = x
(3 x -6x) + (3 x -6) = x
-18x - 18 = x
-18x - 18 - x = 0
-18x - x = 18
-19x = 18
x = \( \frac{18}{-19} \)
x = -\(\frac{18}{19}\)

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 2 x 4) + (2 x 4 x 7) + (2 x 2 x 7)
sa = (16) + (56) + (28)
sa = 100

A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

A trapezoid is a quadrilateral with one set of parallel sides.