You have 12 out of the total of 300 raffle tickets sold so you have a (\( \frac{12}{300} \)) x 100 = \( \frac{12 \times 100}{300} \) = \( \frac{1200}{300} \) = 4% chance to win the raffle.

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

\( \frac{1}{6} \) x \( \frac{3}{5} \) = \( \frac{1 x 3}{6 x 5} \) = \( \frac{3}{30} \) = \(\frac{1}{10}\)

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 10 workers at the company now and that's enough to staff 5 crews so there are \( \frac{10}{5} \) = 2 workers on a crew. 9 crews are needed for the busy season which, at 2 workers per crew, means that the roofing company will need 9 x 2 = 18 total workers to staff the crews during the busy season. The company already employs 10 workers so they need to add 18 - 10 = 8 new staff for the busy season.

The equation for this sequence is:

a_n = a_n-1 + 2(n - 1)

where n is the term's order in the sequence, a_n is the value of the term, and a_n-1 is the value of the term before a_n. This makes the next number:

a₆ = a₅ + 2(6 - 1)
a₆ = 21 + 2(5)
a₆ = 31

To subtract these fractions, first find the lowest common multiple of their denominators. The first few multiples of 9 are [9, 18, 27, 36, 45, 54, 63, 72, 81, 90] and the first few multiples of 15 are [15, 30, 45, 60, 75, 90]. The first few multiples they share are [45, 90] making 45 the smallest multiple 9 and 15 share.

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

\( \frac{6 x 5}{9 x 5} \) - \( \frac{9 x 3}{15 x 3} \)

\( \frac{30}{45} \) - \( \frac{27}{45} \)

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

\( \frac{30 - 27}{45} \) = \( \frac{3}{45} \) = \(\frac{1}{15}\)