The length of the movie is the independent variable x. For every x value, we determine the correspondant y value by evaluating the function.
So, we're given a specific input (x=70), and we want its ouput: we just need to plug x=70 in the equation:
[tex] y = -0.414\cdot 70 + 106.55 = -28.98+ 106.55 = 77.57 [/tex]
This value can be rounded to 78%.
