propositions and logic help

Hi

I am having trouble understanding some subjects in maths, and seem unable to find similar examples elsewhere. I do not want to cheat, nor do this without understanding how it works, so I am hoping that someone can give me some ideas to help me figure this one out alone.

The question is:

*if* P *then* Q

*if not* R *then not* Q

P *or* R

*Therefore,* R.

I need to create a truth table or "any other method that works" to show that this argument is valid.

It may be a big ask, but I would really appreciate it if no one writes an answer so much as perhaps put this into a sentence so I may better understand it. As an example:

P= Eat your vegetables

Q= You will get dessert

I am not sure how R fits into this proposition, any help greatly appreciated!!

Also how/where can I get software or fonts which allow me to type the proper symbols and create tables so I can do this on my PC? Thanks!