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 volume of a cube is height x length x width:

v = h x l x w
v = 3 x 4 x 7
v = 84

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.)

-2a(a - x)
-2(8)(8 + 7)
-2(8)(15)
(-16)(15)
-240

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

5a + 9a = 14a

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.

(7a)(8ab) + (7a²)(9b)
(7 x 8)(a x a x b) + (7 x 9)(a² x b)
(56)(a¹⁺¹ x b) + (63)(a²b)
56a²b + 63a²b
119a²b