Miss Magee has to drive 7 1/2 km to get to school. On Monday she drove to school and arrived at 8:00am, she realized she'd forgotten her laptop, drove back home picked up the laptop, then returned to school.
How far did she drive before school started?

15km

Explanation:

7 1/2 pluse (im new but know a alot of math)7 1/2 equals 15km

Density increases as mass increases, vice versa
Density increases as volume decreases, vice versa
This is because mass, the numerator of the equation, would cause the final answer (density) to increase when it increases, assuming the volume remains constant
And when the denominator of a fraction is large, in this case volume, it would cause the final answer to become smaller!