a. To build the airport at the same distance from the center of each town, they should locate the intersection of the perpendicular bisectors of the segments connecting each pair of towns. The precise location of the airport will be the point where these perpendicular bisectors intersect. This point will be equidistant from the center of each town.
b. To build the airport at the same distance from each road connecting the towns, they should locate the intersection of the angle bisectors of the angles formed by the roads at each town. The precise location of the airport will be the point where these angle bisectors intersect. This point will be equidistant from each road connecting the towns.
Alternatively, they could locate the intersection of the medians of the triangle formed by the three towns. The medians are the segments connecting each vertex of the triangle with the midpoint of the opposite side. The precise location of the airport will be the point where these medians intersect, which is also the centroid of the triangle. This point will be equidistant from each of the three towns.