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 20 workers at the company now and that's enough to staff 5 crews so there are \( \frac{20}{5} \) = 4 workers on a crew. 7 crews are needed for the busy season which, at 4 workers per crew, means that the roofing company will need 7 x 4 = 28 total workers to staff the crews during the busy season. The company already employs 20 workers so they need to add 28 - 20 = 8 new staff for the busy season.

If the tiger has consumed 60 pounds of food in 10 days that's \( \frac{60}{10} \) = 6 pounds of food per day. The tiger needs to consume 84 - 60 = 24 more pounds of food to reach 84 pounds total. At 6 pounds of food per day that's \( \frac{24}{6} \) = 4 more days.

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:

6x⁷ + 2x⁷
(6 + 2)x⁷
8x⁷

To multiply fractions, multiply the numerators together and then multiply the denominators together:

\( \frac{3}{9} \) x \( \frac{2}{7} \) = \( \frac{3 x 2}{9 x 7} \) = \( \frac{6}{63} \) = \(\frac{2}{21}\)

The number of students taking German or Spanish is 8 + 9 = 17. Of that group of 17, 3 are taking both languages so they've been counted twice (once in the German group and once in the Spanish group). Subtracting them out leaves 17 - 3 = 14 who are taking at least one language. 23 - 14 = 9 students who are not taking either language.