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)(8ab) - (6a²)(2b)
(5 x 8)(a x a x b) - (6 x 2)(a² x b)
(40)(a¹⁺¹ x b) - (12)(a²b)
40a²b - 12a²b
28a²b

Parallel lines are lines that share the same slope (steepness) and therefore never intersect. A transversal occurs when a set of parallel lines are crossed by another line. All of the angles formed by a transversal are called interior angles and angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°) and are called corresponding angles. Alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°) and 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°).

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 13cm + 6cm + 6cm = 25cm

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(6²) + 2π(6 x 6)
sa = 2π(36) + 2π(36)
sa = (2 x 36)π + (2 x 36)π
sa = 72π + 72π
sa = 144π

A cube is a rectangular solid box with a height (h), length (l), and width (w). The volume is h x l x w and the surface area is 2lw x 2wh + 2lh.