Recall: distance = rate times time.
To determine how far apart the two cars will be after four hours of travel, subtract the sum of the distances traveled from 200 mi:
Distance apart after four hours = 200 mi - (40 mph)(4 hrs) - (35 mph)(4 hrs)
= 200 mi - 160 mi - 140 mi = -100 mi
The wording of your question implies that the cars will not yet have met after four hours of travel. This negative result is absurd. Please ensure that you have copied down the problem completely and accurately.