After robbing a bank in Dodge City, a robber gallops off at 14 mi/h. 20 minutes later, the marshall leaves to pursue the robber at 16 mi/h. How long (in hours) does it take the marshall to catch up to the robber?

let t = the time from when the robber leaves the bank to when he his captured. Then t - 1/3 = the time it takes for the marshall to catch up. (20 minutes = 1/3 hours)

Since Rate * Time = distance, and the distance travelled is equal, then

14 mi/h * (t ) = 16 mi/h * (t - 1/3)

Simplify, collect like terms , and solve for t.