The two women started at the same time and walked with constant (but not the same) velocity. If sunrise was "x" hours before noon then the first woman walked for 4+ x hours and the second for x+ 9 hours. Let the distance from A to B be "d" km. The first womans speed was d/(x+ 4) km/hour and the second's d/(x+ 9).
They met at noon- x hours after starting. The first woman walked dx/(x+4) km in that time and the second woman walked dx/(x+9) km. Since they met at noon, the total distance walked was d km: You can divide through by d to cancel it and have a single equation left to solve for x.
That's pretty good for two "old women"!