How do you calculate correctly with real world measurements

The vet charges $45 for an office visit and $10 for each vaccination your dog needs. write an eaquation

F(x) = 1/x g(x)=x-4 can you evaluate (g*f)(0) ? why or why not?

Meg constructed triangle poq and then used a compass and straightedge to accurately construct line segment os, as shown in the figure below, which could be the measures of angles pos and angle poq?