Parallel lines are lines that share the same slope (steepness) and therefore never intersect. A transversal occurs when a set of parallel lines are crossed by another line. All of the angles formed by a transversal are called interior angles and angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°) and are called corresponding angles. Alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°) and all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other. Same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°).

When solving an equation with two variables, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

To factor a quadratic expression, apply the FOIL method (First, Outside, Inside, Last) in reverse. First, find the two Last terms that will multiply to produce -12 as well and sum (Inside, Outside) to equal -4. For this problem, those two numbers are -6 and 2. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 4y - 12
y² + (-6 + 2)y + (-6 x 2)
(y - 6)(y + 2)

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 3 + 8 + 9 + 5
p = 25