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.

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 z° = 20, the value of a° is 20.

The formula for area is πr²:

a = πr²
a = π(2²)
a = 4π

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 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.

-6x + 6 > \( \frac{x}{4} \)
4 x (-6x + 6) > x
(4 x -6x) + (4 x 6) > x
-24x + 24 > x
-24x + 24 - x > 0
-24x - x > -24
-25x > -24
x > \( \frac{-24}{-25} \)
x > \(\frac{24}{25}\)