the question is asking for a point at which the two values would intersect, so i think that it is looking for a solution. in this case, i would solve the equations: y=0.15x+19 and y=0.19x.
the point of intersection for these equations is (475, 90.25). you are looking for the x value, so the answer would be 425 minutes of calling for the two plans’ costs to be equal.