The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

When solving an equation with two variables, 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 quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.

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) + (5a²)(5b)
(5 x 8)(a x a x b) + (5 x 5)(a² x b)
(40)(a¹⁺¹ x b) + (25)(a²b)
40a²b + 25a²b
65a²b

To solve this equation, isolate the variable for which you are solving (a) on one side of the equation and put everything else on the other side.

-6a - z = -3a + 3z - 5
-6a = -3a + 3z - 5 + z
-6a + 3a = 3z - 5 + z
-3a = 4z - 5
a = \( \frac{4z - 5}{-3} \)
a = \( \frac{4z}{-3} \) + \( \frac{-5}{-3} \)
a = -1\(\frac{1}{3}\)z + 1\(\frac{2}{3}\)