You can
put this solution on YOUR website!HERE WE NEED TO FIND THE SLOPES BETWEEN ALL POINTS.
(180-170)/(72-70)=10/2=5
(190-170)/(74-70)=20/4=5
(190-180)/(74-72)=10/2=5
BECAUSE THE SLOPE IS 5 FOR ALL LINES THEN THE 3 POINTS ARE ON THE SAME LINE THUS THESE 3 POINTS FORM A LINEAR LINE.