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 line segment is a portion of a line with a measurable length. The midpoint of a line segment is the point exactly halfway between the endpoints. The midpoint bisects (cuts in half) the line segment.

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.

4a - 4a = 0a

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(3²) + 2π(3 x 9)
sa = 2π(9) + 2π(27)
sa = (2 x 9)π + (2 x 27)π
sa = 18π + 54π
sa = 72π

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 > sign and the answer on the other.

7z + 7 > 1 - z
7z > 1 - z - 7
7z + z > 1 - 7
8z > -6
z > \( \frac{-6}{8} \)
z > -\(\frac{3}{4}\)