A student used points (150,80) and (50,30) but wrote the equation y=5x + 0.5. What mistake did the student make?

Answer 1

Use:
(y-y1)=(x-x1)(y2-y1)/(x2-x1)

Substitute (x1,y1)=(50,30) and (x2,y2)=(150,80).

When you get the right answer, the mistake is obvious. And simple.