Using the two known points we can see that the slope of the line is 1/2.
How to find the slope of the line?
If a line passes through two given points (x₁, y₁) and (x₂, y₂), then the slope is given by:
a = (y₂ - y₁)/(x₂ - x₁,)
Here we can use the first and the last points, which are (1, 3) and (9, 7), then we will get the slope:
a = (7 - 3)/(9 - 1) = 4/8 = 1/2
The slope is 1/2.