The greatest common factor of two numbers, one of which is 1, will always be 1.
X by its self is always 1x
1x+8=-15 you have to get rid of 8 by subtracting on both sides
1x=-23 now get rid of 1 by dividing on both sides
x=-23
13. Because it can't be divided by a whole number except 1 and itself. 14 can be Divided by 2. 21 and 33 can be divided by 3 making them composite or divisible by more than just 1 and itself :)
25 is the number. Hope this helps.
