What is the equation of the line containing the points 7 3 and 14 6 and 21 9?

The slope of the line is (6-3)/(14-7) = 3/7

The equation is:

y - 3 = (3/7)(x - 7)

→ y - 3 = (3/7)x - 3

← y = (3/7)x