The document contains several problems related to differential equations: 1) It describes the location of a car over time based on its initial location and velocity formula. It asks to find the car's velocity at t=1 and location at t=5. 2) It asks to find a function that satisfies the differential equation f(x)f'(x)=x with the initial condition f(0)=1. 3) It asks to model the decay of radium over time based on its initial amount and decay rate, and express the amount remaining after t years.