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.

A cylinder is a solid figure with straight parallel sides and a circular or oval cross section with a radius (r) and a height (h). The volume of a cylinder is π r²h and the surface area is 2(π r²) + 2π rh.

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.

-6a - 6 = \( \frac{a}{-8} \)
-8 x (-6a - 6) = a
(-8 x -6a) + (-8 x -6) = a
48a + 48 = a
48a + 48 - a = 0
48a - a = -48
47a = -48
a = \( \frac{-48}{47} \)
a = -1\(\frac{1}{47}\)

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 9 x 7) + (2 x 7 x 1) + (2 x 9 x 1)
sa = (126) + (14) + (18)
sa = 158

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.