In this you’re just finding the values of the function for the given x values.
f(0) is the y value when x=0, so you look at the graph at x=0 and look at what y value is at the point. At x=0 you get y=1, so f(0)=1.
Same thing with the other function. g(-8)= -6.
Then you substitute those values.
-8(1) + 4(-6) = -8-24 = -32
