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.

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.

-3y - 7 < \( \frac{y}{9} \)
9 x (-3y - 7) < y
(9 x -3y) + (9 x -7) < y
-27y - 63 < y
-27y - 63 - y < 0
-27y - y < 63
-28y < 63
y < \( \frac{63}{-28} \)
y < -2\(\frac{1}{4}\)

To solve this equation, 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.)

7c(c - x)
7(5)(5 - 2)
7(5)(3)
(35)(3)
105

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.

2y - 3 = \( \frac{y}{-8} \)
-8 x (2y - 3) = y
(-8 x 2y) + (-8 x -3) = y
-16y + 24 = y
-16y + 24 - y = 0
-16y - y = -24
-17y = -24
y = \( \frac{-24}{-17} \)
y = 1\(\frac{7}{17}\)