Dependent variable is dependent on the independent variable
m, because the amount of tread lost depends on how many miles you traveled
it's not, the amount of miles depends on how much tread you lost
m is indepdent
First one is 6*5*4*3*2*4*3*2
second is 5*4*3*2*2
The volume of a cylinder is given by

Let
and 
The new volume becomes

So, the new volume is 8 times the original volume. In fact, volume scales linearly with the height and quadratically with the radius.
Larger negative numbers are less than, if you picture a number line.
<.......-83 ............-38........0........+38..........>
-83 < -38
The canyon is deeper or has a lower elevation than the scuba diving location.