Average speed in miles per hour is the number of miles traveled divided by the number of hours:

Solving for time:

time = \( \frac{\text{distance}}{\text{speed}} \)
time = \( \frac{105mi}{15mph} \)
7 hours

To subtract these fractions, first find the lowest common multiple of their denominators. The first few multiples of 4 are [4, 8, 12, 16, 20, 24, 28, 32, 36, 40] and the first few multiples of 8 are [8, 16, 24, 32, 40, 48, 56, 64, 72, 80]. The first few multiples they share are [8, 16, 24, 32, 40] making 8 the smallest multiple 4 and 8 share.

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

\( \frac{3 x 2}{4 x 2} \) - \( \frac{7 x 1}{8 x 1} \)

\( \frac{6}{8} \) - \( \frac{7}{8} \)

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

\( \frac{6 - 7}{8} \) = \( \frac{-1}{8} \) = -\(\frac{1}{8}\)

To fill a 25 gallon tank exactly halfway you'll need 12\(\frac{1}{2}\) gallons of fuel. Each fuel can holds 2\(\frac{1}{2}\) gallons so:

cans = \( \frac{12\frac{1}{2} \text{ gallons}}{2\frac{1}{2} \text{ gallons}} \) = 5

If 90% of the town's 16,000 voters cast ballots the number of votes cast is:

(\( \frac{90}{100} \)) x 16,000 = \( \frac{1,440,000}{100} \) = 14,400

The mayor got 74% of the votes cast which is:

(\( \frac{74}{100} \)) x 14,400 = \( \frac{1,065,600}{100} \) = 10,656 votes.

To take the square root of a fraction, break the fraction into two separate roots then calculate the square root of the numerator and denominator separately:

\( \sqrt{\frac{64}{25}} \)
\( \frac{\sqrt{64}}{\sqrt{25}} \)
\( \frac{\sqrt{8^2}}{\sqrt{5^2}} \)
\( \frac{8}{5} \)
1\(\frac{3}{5}\)