Alg 2 question for umm... I forgot. c;

So um... the top part is just a visual to myself to see what the question is asking for. I might have gotten rates mixed up but that doesn't matter.
Okay, well the chart is just there to organize my thoughts.  Basically the equations (based off of d=rt) I can make from the given information are:
(because idk how to do subscripts here, let a= the first "time". Let b= the second length of time.)
d=45a
d=40b
Oh, and I guess I better clear up that d=x.
Okay, so. According to the chart, if:
a+b=4 (hours) <----plug this into "t"
Then x+x=2x. <----- plug this into "d"
And we also add the rates! (40+45=85 mph) <----- plug this into "r"
So we plug all those values into the formula d=rt, and we get
2x=(85)4
2x=340
x=170.

Believe me, just looking at the work is a LOT simpler than how I explained this.  Look for me before school tomorrow if you still don't get it! I can probably explain it a lot better face to face than on here... gomenasai!  >.<

Well, now that I've read all my manga updates (Goong was so awesome omgomgomgomgomg!!!) I am now going to actually do my own homework... that is, the opening statements for mock trial, the  chem worksheet + studying for the chem test, ch 3 cornell notes for history, my TRF forms, read and review the acadec section for my lecture tomorrow, oh and not to mention ALL questions, summaries, and learning logs for the last week and a half. *sigh* They work us like dogs here...