We calculate the speed by dividing the distance over time: s = d/t So the distance described in the problem is always the same, A to B and B to A. But we are told that; 7 = d/t 7 = 2d/(t + 2) that is, the first equation say that at speed 7 km/h a distance d is walked in a time t the second equation say that at a average speed of 7 (that is 8 on one way and 6 in the other: 8 + 6 = 14, half of it), twice the distance is walked in a time equal to the first time plus 2 minutes. So we have a system of linear equations, 2 of them with two unknowns, we can solve that: 7 = d/t 7 = 2d/(t + 2<span>) </span>lets simplify them: 7t = d 7(t + 2) = 2d 7t = 2d - 14 we substitute the first in the second: <span>7t = 2d - 14 </span><span>7t = d </span>so: d = 2d - 14 d = 14 so the distance between A and B is 14 km
