In order to find how many additional workers are needed to staff the extra crews you first need to calculate how many workers are on a crew. There are 16 workers at the company now and that's enough to staff 4 crews so there are \( \frac{16}{4} \) = 4 workers on a crew. 9 crews are needed for the busy season which, at 4 workers per crew, means that the roofing company will need 9 x 4 = 36 total workers to staff the crews during the busy season. The company already employs 16 workers so they need to add 36 - 16 = 20 new staff for the busy season.

To multiply terms with exponents, the base of both exponents must be the same. In this case they are so multiply the coefficients and add the exponents:

-3z⁴ x 2z⁴
(-3 x 2)z^{(4 + 4)}
-6z⁸

To add or subtract terms with exponents, both the base and the exponent must be the same. In this case they are so add the coefficients and retain the base and exponent:

-3b⁷ + 4b⁷
(-3 + 4)b⁷
b⁷

Use PEMDAS (Parentheses, Exponents, Multipy/Divide, Add/Subtract):

2 + (4 + 2) ÷ 4 x 5 - 5²
P: 2 + (6) ÷ 4 x 5 - 5²
E: 2 + 6 ÷ 4 x 5 - 25
MD: 2 + \( \frac{6}{4} \) x 5 - 25
MD: 2 + \( \frac{30}{4} \) - 25
AS: \( \frac{8}{4} \) + \( \frac{30}{4} \) - 25
AS: \( \frac{38}{4} \) - 25
AS: \( \frac{38 - 100}{4} \)
\( \frac{-62}{4} \)
-15\(\frac{1}{2}\)

There are 4 2-passenger taxis available so that's 4 x 2 = 8 total seats. There are 12 people needing transportation leaving 12 - 8 = 4 who will have to find other transportation.