Aaron starts walking at a rate of 3 mi/h on a road toward a store 10 mi away. zhang leaves the store when aaron starts walking, and he walks toward aaron along the same road at 2 mi/h. how many hours will pass before they meet?

The first thing you should do is write the equation of the position for each person. After having them you must match them because they will be in the same position when they are at a point. After equalizing you clear the time. Attached solution.
The solution is t=2 hours.