Question

Assume two lines do not coincide (~q). Then, either their slopes are different or their y-intercepts are different (~p). Since ~q → ~p is true, p → q must be true. Therefore, if the slopes and y-intercepts are the same, then two lines coincide.

Answer 1

@dan815

Answer 2

if slopes and y intercepts are same, the lines coincide with infinite solutions
if slopes are same, but y intercepts different, lines are parallel with no solution
if slopes are different and y intercepts different, then there is 1 solution