We create a system of equations.
Jeremy:
y = 7 + 1x
Tony:
y = 3 + 2x
Where 'y' is the total miles, and 'x' is the number of weeks.
To find out when they will be running the same distance, we find the point of intersection between these two, which is (4, 11).
So in 4 weeks both Jeremy and Tony will be running the same distance, which is 11 miles.