Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).

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 coordinate grid is composed of a horizontal x-axis and a vertical y-axis. The center of the grid, where the x-axis and y-axis meet, is called the origin.

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(3a)(6ab) + (3a²)(6b)
(3 x 6)(a x a x b) + (3 x 6)(a² x b)
(18)(a¹⁺¹ x b) + (18)(a²b)
18a²b + 18a²b
36a²b

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.

-7x + 5 = \( \frac{x}{9} \)
9 x (-7x + 5) = x
(9 x -7x) + (9 x 5) = x
-63x + 45 = x
-63x + 45 - x = 0
-63x - x = -45
-64x = -45
x = \( \frac{-45}{-64} \)
x = \(\frac{45}{64}\)