A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 7 x 7 = \( \frac{49}{2} \) = 24\(\frac{1}{2}\)

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:

(y + 4)(y - 7)
(y x y) + (y x -7) + (4 x y) + (4 x -7)
y² - 7y + 4y - 28
y² - 3y - 28

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.)

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.

9y - 9 < \( \frac{y}{9} \)
9 x (9y - 9) < y
(9 x 9y) + (9 x -9) < y
81y - 81 < y
81y - 81 - y < 0
81y - y < 81
80y < 81
y < \( \frac{81}{80} \)
y < 1\(\frac{1}{80}\)