Please please please please help

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

Bring the fraction a/a-4 to a denominator of 16-a^2

Solve the problem by making up an equation. a man could arrive on time for an appointment if he drove the car at 40 mph; however, since he left the house 15 minutes late, he drove the car at 50 mph and arrive 3 minutes early for the appointment. how far from his house was his appointment?