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:

-4c⁴ - 7c⁴
(-4 - 7)c⁴
-11c⁴

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

\( \frac{3}{8} \) x \( \frac{4}{6} \) = \( \frac{3 x 4}{8 x 6} \) = \( \frac{12}{48} \) = \(\frac{1}{4}\)

To multiply terms with radicals, multiply the coefficients and radicands separately:

8\( \sqrt{8} \) x 4\( \sqrt{6} \)
(8 x 4)\( \sqrt{8 \times 6} \)
32\( \sqrt{48} \)

Now we need to simplify the radical:

32\( \sqrt{48} \)
32\( \sqrt{3 \times 16} \)
32\( \sqrt{3 \times 4^2} \)
(32)(4)\( \sqrt{3} \)
128\( \sqrt{3} \)

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

Solving for distance:

distance = \( \text{speed} \times \text{time} \)
distance = \( 65mph \times 2h \)
130 miles

To simplify this fraction, first find the greatest common factor between them. The factors of 28 are [1, 2, 4, 7, 14, 28] and the factors of 60 are [1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60]. They share 3 factors [1, 2, 4] making 4 their greatest common factor (GCF).

Next, divide both numerator and denominator by the GCF:

\( \frac{28}{60} \) = \( \frac{\frac{28}{4}}{\frac{60}{4}} \) = \( \frac{7}{15} \)