For parallel lines with a transversal, the following relationships apply:

• angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°)
• alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°)
• 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°)

Applying these relationships starting with c° = 21, the value of z° is 21.

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

x² - 10x + 16 = 0
(x - 2)(x - 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (x - 2) or (x - 8) must equal zero:

If (x - 2) = 0, x must equal 2
If (x - 8) = 0, x must equal 8

So the solution is that x = 2 or 8

A monomial contains one term, a binomial contains two terms, and a polynomial contains more than two terms.

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.

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