The answer is -8 because if you do the math
By solving for x you get x=6
It would be 21 because 7 times 3 equals 21 and the way you get that is 3 drawings per paper
The only math term I can think of is geometry and it means when a solid is cut through parallel to the base.
EDIT: After further research since it was all I could think of. This is the only math term for what you are looking for.
If we have the speed of 18 miles per second, 18miles/s
to find out what is the speed in 1 minute we will need to multiply 18 by 60, as there are 60 seconds in 1 minute
18 miles..............................1 second
?miles..................................60 seconds(1min)
18*60=1080 miles
we have 1080 miles/minute
in 2 minutes we have 1080*2=2160 miles
hope it helps