65 total test items were on the test.
11/131 is 0.084, 8.4% or 8%.
ANSWER
The function if the graph is,

EXPLANATION
We want to write the function for the graph that, goes through (1,8) and (0,2).
Let the function be of the form

Where m is the slope and

is the y-intercept.
The slope is

The equation becomes,