Problem explained and solved on attached document. Additional examples are given. Enjoy!
m is short for slope. And all you have to do is take the two y's which in this case are -1 and 8; and the x's: 4 and 3. So now you have to do this -1-8 and you should get -9, then subtract 4 from(4-3) and you should get 1. Therfore your final answer should be m=-9.