By buying two shirts, Charlie will save $30 x \( \frac{45}{100} \) = \( \frac{$30 x 45}{100} \) = \( \frac{$1350}{100} \) = $13.50 on the second shirt.

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. 10 crews are needed for the busy season which, at 4 workers per crew, means that the roofing company will need 10 x 4 = 40 total workers to staff the crews during the busy season. The company already employs 20 workers so they need to add 40 - 20 = 20 new staff for the busy season.

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

3x⁵ - 5x⁵
(3 - 5)x⁵
-2x⁵

A ratio of 4:1 means that there are 4 home fans for every one visiting fan. So, of every 5 fans, 4 are home fans and \( \frac{4}{5} \) of every fan in the stadium is a home fan:

31,000 fans x \( \frac{4}{5} \) = \( \frac{124000}{5} \) = 24,800 fans.

To add these fractions, first find the lowest common multiple of their denominators. The first few multiples of 5 are [5, 10, 15, 20, 25, 30, 35, 40, 45, 50] and the first few multiples of 9 are [9, 18, 27, 36, 45, 54, 63, 72, 81, 90]. The first few multiples they share are [45, 90] making 45 the smallest multiple 5 and 9 share.

Next, convert the fractions so each denominator equals the lowest common multiple:

\( \frac{4 x 9}{5 x 9} \) + \( \frac{2 x 5}{9 x 5} \)

\( \frac{36}{45} \) + \( \frac{10}{45} \)

Now, because the fractions share a common denominator, you can add them:

\( \frac{36 + 10}{45} \) = \( \frac{46}{45} \) = 1\(\frac{1}{45}\)