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.

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.

2a + 7z = 5a - 4z - 6
2a = 5a - 4z - 6 - 7z
2a - 5a = -4z - 6 - 7z
-3a = -11z - 6
a = \( \frac{-11z - 6}{-3} \)
a = \( \frac{-11z}{-3} \) + \( \frac{-6}{-3} \)
a = 3\(\frac{2}{3}\)z + 2

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.

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

sa = 2πr² + 2πrh
sa = 2π(9²) + 2π(9 x 7)
sa = 2π(81) + 2π(63)
sa = (2 x 81)π + (2 x 63)π
sa = 162π + 126π
sa = 288π

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.

-9b + 7 = 6 - 5b
-9b = 6 - 5b - 7
-9b + 5b = 6 - 7
-4b = -1
b = \( \frac{-1}{-4} \)
b = \(\frac{1}{4}\)