It will take 20 seconds to move from one end to another because if 20 feet is moved within 5 seconds, do that 4 more times to get to 80. Finally, multiply 5 by 4 to get 20 seconds.
If you mean this one then:
Yes it is a perfect square, since you get a whole number as the original points
And the answer is C
The next step in this problem would be to subtract 12 form both sides. This would result in:
-4x = - 16
Then you would divide each side by -4.
x = 4
This would be your answer.