#### Answer

a) 350 km.
b) 78 km/h.

#### Work Step by Step

a. Calculate the time for the first part of the trip.
$$\Delta t = \frac{180 km}{95 km/h} = 1.895 hours$$
The time for the second leg of the trip is the remainder, 2.605 hours.
Find the distance for the second leg of the trip.
(65 km/h)(2.605 h) = 169.3 km.
The total distance is the sum of the distances for the two legs.
b. The definition of average speed is the total distance over the time.
$$\frac{350 km }{4.5 h} = 78 km/h$$