We know that the two cars combined will have traveled 295 miles at the time they pass each other.
We also know that both cars left in the pm. Please always watch for that very carefully--a very easy oversight.
295 miles=(50 miles/hour)(x hours)+(40 miles/hour)[(x-0.50) hours]
Please note the fact that I indicated the time of (x-0.50) hours, not minutes.
Before we make any calculations, we must be certain that the units are align.
Let's cancel the hours which are both the numerators and denominators on the right side of the equation...
295 miles=(50 miles/hour)(x
295 miles=(50 miles)(x)+(40 miles)(x-0.50)
Let's cancel the miles...
Let's add 20 to both sides as we proceed to isolate x...
Let's divide both sides by 90...
At 3.5 hours from the departure time of the first car, these will pass.
The first car departed at 1 pm.