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.

(3a)(9ab) - (5a²)(9b)
(3 x 9)(a x a x b) - (5 x 9)(a² x b)
(27)(a¹⁺¹ x b) - (45)(a²b)
27a²b - 45a²b
-18a²b

A monomial contains one term, a binomial contains two terms, and a polynomial contains more than two terms.

An equation is two expressions separated by an equal sign. The key to solving equations is to repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

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.

You need to find the value of b so solve the first equation in terms of y:

-b + y = 5
y = 5 + b

then substitute the result (5 - -1b) into the second equation:

5b - 3(5 + b) = -9
5b + (-3 x 5) + (-3 x b) = -9
5b - 15 - 3b = -9
5b - 3b = -9 + 15
2b = 6
b = \( \frac{6}{2} \)
b = 3