Factoring out variables?

Question

I'm in algebra II right now and some of my basic algebra has been a little lost on me over the summer. I don't have my book with me, help me figure out this question or at least tell me out to set it up

Two buses leave houston at the same time and travel in opposite directions. One bus averages 55mph the other 45mph. When will they be 400 mi apart?

so far all I can remember is 45x+55y=400 tell me if that right and how can i factor out the y?

Answer 1

Although you do have the right idea to solve this problem, you forgot to realize that x = y.  I worked it out below using only one variable.

First bus is traveling 55mph.

Second bus is traveling 45mph in opposite direction.

When they are 400 miles apart, they both would have taken the same amount of time (T).

When they are 400 miles apart,

first bus will have traveled 55T miles

second bus will have traveled 45T miles

and

55T + 45T = 400 miles

100T = 400

T = 400/100 = 4 hours