Two hikers start from the same point and hike in opposite directions around a lake whose shoreline is 17 mi long. one hiker walks 0.5 mph faster than the other hiker. how fast did each hiker walk if they meet in 2 h?

Let A be the speed of hiker A and B the speed of hiker B.
let's say that B is faster than A, so B=A+0.5
we know that they met after 2 hours, and the distance each walked after 2 hours is given by:

One of the hikers travels at 4 miles per hour, the other one at 4.5 miles per hour

What am i doing here. add?