If you are trying to factor it is 14(3a+b).
But if you are looking for the greatest common factor it is 14.
The simple way of calculating a perimeter is to add all of the sides.
For a rectangle this would equal 2 x length + 2 x width
P = 2(6x + 3) + 2(-2x - 5)
= 12x + 6 - 4x - 10
= 8x - 4
At a higher level both the length and width must be greater than zero (= zero is a trivial rectangle)
6x + 3 > 0
6x > -3
x > -0.5
-2x - 5 > 0
2x + 5 < 0 (multiplying by -1 reverses the inequality)
2x < -5
x < -2.5
This rectangle cannot exist as x cannot be < -2.5 and > -0.5 at the same time!
When dealing with statistics (probabilities of events etc) and histograms
I used a converter so i put 3200 meters into feet which was 10,498.69 and i rounded it to 10,498 and then i subtract 10,498 feet from 11,808 feet and got 1,310 feet as the answer