Question 431195
if in your answer x = 7.5 and x = 12,5 is speed of truck in mountain and flat land then it is wrong.

the speed of truck in flatland will be 50 mph and in mountain it will be 30 mph.

the time taken will be 6 hours by both.

speed = distance / time

let the time taken be x hours

s = 300/x

s - 20 = 180/x

equating both we get

300/x - 20= 180/x

x = 6 hours.

replacing value of x we get speed for truck.