We already have the equation that gives us the number of miles Johanna has left on her trip - it is the function f(x):
[tex]f(x)=1084-65t[/tex]where t is the number of hours of driving.
After 12 hours of driving, we have t = 12, putting that into f(x) gives
[tex]f(12)=1084-65(12)[/tex][tex]f(12)=304[/tex]Hence, Johanna has left 304 miles after 12 hours of driving.