a bus is driving through traffic as it makes a number of express stops. the bus drives at a speed of 10 m/s2 for 90 seconds then drives at a speed of 15m/s for 120 seconds before stopping for 30 seconds, then drives at a speed of 5m/s for 60 seconds before stopping for 15 seconds. Find the average speed of the during the trip.

10m/s^2 is acceleration an not speed.

Did you mean 10m/s?

D = 10*90 + 15*120 + 5*60,
D = 900 + 1800 + 300 = 3000m = total distance.

T = 90 + 120 + 30 + 60 + 15 = 315s.

V = D / T = 3000m / 315s = 9.52m/s.