Given points are

Next, find the slope.

Substitute 20.5 for y₂,  7 for y₁, 1 for x₂, and 3.5 for x₁  in slope formula.

                         (Subtract: )

                              (Subtract: ) \ \

                                               (Divide: )

You know the slope and a point on the line, so use point - slope form

with either given point to write an equation of line.

Choose

                  (Substitute 7 for y₁, 3.5 for x₁ and )

           (Apply distributive property: )

                  (Multiply: )

      (Add 7 to each side)

            (Apply additive inverse property: )

                  (Apply additive identity property: )

                                (Add: )

The equation of line is .