How to solve this physics problem?

two knights on horseback start from rest at 86meters apart and ride directly toward each other to do battle. George's acceleration has a magnitude of 0.15m/s^2, while Alfred's has a magnitude of 0.3m/s^2. How far from George's starting point do the knights collide? The answer is 28.7m but i can't figure out how to do it and i need to show my work. Thanks!