A line on the coordinate grid can be defined by a slope-intercept equation: y = mx + b. For a given value of x, the value of y can be determined given the slope (m) and y-intercept (b) of the line. The slope of a line is change in y over change in x, \({\Delta y \over \Delta x}\), and the y-intercept is the y-coordinate where the line crosses the vertical y-axis.

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.

-8z + 9 > \( \frac{z}{7} \)
7 x (-8z + 9) > z
(7 x -8z) + (7 x 9) > z
-56z + 63 > z
-56z + 63 - z > 0
-56z - z > -63
-57z > -63
z > \( \frac{-63}{-57} \)
z > 1\(\frac{2}{19}\)

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.

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 4 + 1 + 4 + 2
p = 11

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².