Need help with my geometry homework

Okay so I got this homework right... Yeah you all know what I mean.

But I can't make heads or tails of how to do it.

I'm not going to post it all, just a question and I'll figure out how to do the rest of it if someone helps with this one.

Now here is the first one. I really don't need the answer, just the formula (and/or how to do it if there is no given formula).

Use the given endpoint R and midpoint M of RS(Has a line segment sign over it) to find the coordinates of the other endpoints.

R(6,0), Midpoint (0,2)