Average speed in miles per hour is the number of miles traveled divided by the number of 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 10 are [10, 20, 30, 40, 50, 60, 70, 80, 90]. The first few multiples they share are [20, 40, 60, 80] making 20 the smallest multiple 4 and 10 share.

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

\( \frac{7 x 5}{4 x 5} \) - \( \frac{8 x 2}{10 x 2} \)

\( \frac{35}{20} \) - \( \frac{16}{20} \)

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

\( \frac{35 - 16}{20} \) = \( \frac{19}{20} \) = \(\frac{19}{20}\)

To find the average of these 4 numbers add them together then divide by 4:

\( \frac{9 + 3 + 8 + 4}{4} \) = \( \frac{24}{4} \) = 6

A factor is a positive integer that divides evenly into a given number. For example, the factors of 8 are 1, 2, 4, and 8.

The first few multiples of 8 are [8, 16, 24, 32, 40, 48, 56, 64, 72, 80] and the first few multiples of 12 are [12, 24, 36, 48, 60, 72, 84, 96]. The first few multiples they share are [24, 48, 72, 96] making 24 the smallest multiple 8 and 12 have in common.