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.

4a⁵ + 8a⁵ = 12a⁵

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.)

To factor a quadratic expression, apply the FOIL method (First, Outside, Inside, Last) in reverse. First, find the two Last terms that will multiply to produce 72 as well and sum (Inside, Outside) to equal -17. For this problem, those two numbers are -9 and -8. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 17y + 72
y² + (-9 - 8)y + (-9 x -8)
(y - 9)(y - 8)

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

a = l x w
a = a x b
a = 3 x 8
a = 24

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

sa = 2πr² + 2πrh
sa = 2π(8²) + 2π(8 x 5)
sa = 2π(64) + 2π(40)
sa = (2 x 64)π + (2 x 40)π
sa = 128π + 80π
sa = 208π