physics
posted by joe .
A golfer rides in a golf cart at an average speed of 3.10 m/s for 29.0 s. She then gets out of the cart and starts walking at an average speed of 1.40 m/s. For how long (in seconds) must she walk if her average speed for the entire trip, riding and walking, is 2.20 m/s?

avg speed= distance/total time
distance=3.1*29 m+1.4*t
2.20=(3.1*29+1.4t)/(29+t)
solve for t.