The distance: use absolute value
Between x and 8: x-8
The distance between x and 8: | x-8 |
“is no more than” means it can be that or be less than that, so use ≤
The distance between x and 8 is no more than 4
| x-8 | ≤ 4
1 inch = 12 miles
so 6 1/2 inches (or 6.5 inches) = 6.5 * 12 = 78 miles <===
Electromagnetic (EM) waves
If you're talking about the second part of the question where it asks you which facts you included in your answer, you can choose any of them and it will be counted right.
The asnwer would be 768 cm^3<span />