If the trip takes 3 hours for a total distance of 350 km, travelling at x hours at 120km/h and remaining time at 60 km/h

x = 2.8 hours

Explanation

Total distance = 350 km

Time period = 3 hrs

Hence we need to formulate an equation ...,

Distance = Speed * Time

; Distance covered travelling at 120 = 120x Since the total time period was 3hrs ... then the remaining time is (3 - x)

; Distance covered travelling at 60 = 60 (3 - x)

The equation is going to be ...,

; 120x + 60 (3 - x) = 350 ... since total distance is 350 km

; 120x + 180 - 60x = 350

; 60x = 170 ... divide both sides by 60

Hence ..., x = 2.8 hours