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

p = x + y + z
p = 7cm + 14cm + 14cm = 35cm

A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.

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.)

-a(a - x)
-1(-7)(-7 + 4)
-1(-7)(-3)
(7)(-3)
-21

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 6 x 8) + (2 x 8 x 1) + (2 x 6 x 1)
sa = (96) + (16) + (12)
sa = 124

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.

(6a)(4ab) + (3a²)(7b)
(6 x 4)(a x a x b) + (3 x 7)(a² x b)
(24)(a¹⁺¹ x b) + (21)(a²b)
24a²b + 21a²b
45a²b