Answer:
Part 18) The railroad ties are parallel
Part 19) One railroad tie is perpendicular to both rails
Explanation:
Part 18) The railroad ties are each perpendicular to one rail
we know that
if one line is perpendicular to several other lines, then the other lines are parallel
Conclusion:
If the railroad ties are each perpendicular to one rail then the railroad ties are parallel
That means----> The slopes of the railroad ties are equal and they are opposite reciprocal of the slope of the rail
Part 19) The rails are parallel. One railroad tie is perpendicular to one rail
we know that
if two lines are parallel and another line is perpendicular to one of them, then this line is perpendicular to both lines
Conclusion:
If One railroad tie is perpendicular to one rail, then one railroad tie is perpendicular to both rails
That means ---> The slopes of the railroad ties are opposite reciprocal to the slope of the rail