OK, here we go
First, remember that they both have to walk 60 feet. Since you do not mention acceleration, I assume that they move at constant speed.
Call the speed of the first person V_1 and the second person V_2. They tell us that V_2 is 12 feet/min faster than V_1 so we have
V_2 = V_1 + 12
Call the time it takes the first person to cover the bridge t. So, the time for the second person is (t-2.5) since the second person started 2.5 minutes sooner.
Now, the distance for person 1 is V_1*t and for person 2 it is V_2*(t-2,5) = (V_1+12)*(t-2.5). Since they both travel the same distance, we can set these two equal so that V_1*t = (V_1+12)*(t-2.5). Solve for V_1.