The distance between two cities is 145 miles. a truck can cover this distance in 2.5 hours. the speed of a car is 1.5 times faster than the speed of the truck. how long does it take them to meet, if they start moving towards each other simultaneously?

It's known that Speed = Distance/Time. The truck can cover the distance of 145 miles in 2.5 hours. So its speed is 145/2.5 = 58 mi/hr. The speed of the car is 1.5 faster than the speed of the track. So the speed of the car is 58*1.5 = 87 mi/hr.  

Let t = amount of time, in hours, it takes them to meet.

The distance that the truck travels in t hours would be 58t miles.
The distance that the car travels in t hours would be 87t miles.
In total they cover the whole distance when they meet. So we get

58t + 87t = 145
145t = 145

Divide both sides by 145:
t = 1

Thus it takes them 1 hour to meet.