Given:
The set of data points on the graph.
To find:
The equation of line that connects the set of data points.
Solution:
From the given graph it is clear that the data points are (20,40), (35,50), (50,60), (65,70).
If a line passes through two points
and
, then the equation of line is

Let as consider the line passes through (20,40) and (50,60), then the equation of line is



Multiply both sides by 3.


Isolate variable terms.


Therefore, the standard form of the required line is
.