Using slope formula
m = (y2 -- y1) / (x2 -- x1)
m= slope
Plug in values, for x1 if you use 4 you must then for x2 use -2 but if you use -2 for x1 you must use 4 for x1, simply, if you go left to right, you cant go right to left on the next one.
m = (3 --4) / (4 --2)
m= 7 / 6