The line that represents the relationship between "y" and "x" passes through the origin and the points (k,7) and (-81,-9)
Assuming that "y" varies directly with "x", we can express their relationship as:

Where "m" represents the slope of the line, also known as coefficient of proportionality or variation.
Using this expression and the known paired values (-81,-9) we can calculate the value of the slope as:

The slope of the line is m=1/9 → this value is constant, regardless the values of x and y. Using it you can determine the value of k as follows:

The value of k is 63