Yeah, where I live, to find the slope (or as we call it, the gradient), you just have to do the two y values subtracted from each other, over the two x values subtracted from each other. The important thing is to remember that if you subtract the first y value from the second (so, 12 - 8), you have to do the same thing for the x (6 - 2)

=

= 1.
The slope is 1.
D
3y=12x
y=4x
the constant is 4 which answers your question
Best to take this in two parts.
1, find the factors of 36:
1 and 36
2 and 18
3 and 12
4 and 9
6 and 6
2, Now, using those, add the factors and see which add up to 15... in this case, that would be 12 and 3!