How do you evaluate f(x)=3×3-4x+5

-- It'll be a lot easier if you clean up the function first.
You're not changing the function.  You're just making it
easier to read and work on without mistakes.

Notice that  3x3=9 ,  so the function is  f(x) = 9 - 4x + 5

Combine like terms, and the function is  f(x) = 14 - 4x .
Much easier to work with.

-- Now, when somebody tells you to evaluate the function for some number,
just take their number, write it in place of 'x',and see what you've got.

Example:

             f(x) = 14 - 4x

             Evaluate  f(x)  for  x = 3.

-- Write 3 in place of 'x' in the function:    f(3) = 14 - 4(3)

--  4(3) = 12 .  So the function is             f(3) = 14 - 12

-- Finish up the subtraction :                  f(3) = 2

You just evaluated  f(x)  for  x=3.
Nice job !

J= r + 9 because since jessica rode 9 more miles than roger, you add 9 miles to rogers mileage.