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.

(5a)(3ab) - (2a²)(2b)
(5 x 3)(a x a x b) - (2 x 2)(a² x b)
(15)(a¹⁺¹ x b) - (4)(a²b)
15a²b - 4a²b
11a²b

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 x° = 153, the value of z° is 27.

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.

The area of a rectangle is equal to its length x width:

a = l x w
a = a x b
a = 8 x 2
a = 16

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 9 + 2 + 6 + 9
p = 26