Let's try to get something that would work for just 5 for now. Any of these numbers would leave a remainder of 1 when divided by just 5: 6, 11, 16, 21, 26, 31, 36, 41, 46, 51, 56, 61, 66, 71, 76, 81, 86, ... Notice that they all look like 5*(something) + 1. Basically, they are all multiples of 5 plus 1.
Let's see what would work for just 8: 9, 17, 25, 33, 41, 49, 57, 65, 73, 81, 89, ...
Are there any matches... AHA! It's 81. This is the lowest positive integer greater than 1 that follows the rule for both 5 and 8.
The length of VW is just the distance between the two coordinates. You could use the distance formula, or an easier and faster way would be to recognize that since both points have the same y-coordinate, the distance between them will just be the distance of the x-coordinates. The absolute value of -4 and -2 is 2, so the length of VW is 2 units.
