First we need to find the base fee by setting up a systems of equation. 47.50 = 150x + b 70 = 300x + b In this, x is number of miles driven and b is the base fee. Isolate x in one of the equations and solve by substitution. 70 = 300x + b -----> Subtracy b from both sides and then divide by 300. x = (70-b)/300 ----> Now plug this into the other equation and solve for b. 47.50 = 150((70-b)/300) + b ----> Simplify and then isolate b. 47.50 = ((70-b)/2) + b 47.50 = 35 - b/2 + b 12.50 = .5b b = 25 Now plug b into one of the equations above to get cost per mile. 70 = 300x + 25 45 = 300x x = .15 Now use these values for your equation. a.) f(x) = .15x + 25 b.) D c.) For this just plug 310 into the equation you made. f(310) = .15(310) + 25 f(310) = $71.5 Hope this helps!
