I'm sorry for all of the questions but i am just lost, I'm thinking that our teacher did not explain this well enough to us. But I have two questions.

Find a number "t" such that the line passing through the 2 given points has a slope of -2.

(t+1,5) (6,-3t+7)

Use slopes to show the points (-4,6) (-1,12) and (-7,0)all lie on the same straight line.

For these I just would like a setup so I can learn how to do these myself