What are unused variables and how can you correct it?

Question

It goes like this: double fine=0.0;The fine is somehow unused.
https://code.sololearn.com/cP445c9D0L7F/?ref=app

Answer 1

You declared variable as "Fine" but using like "fine".
Both are different, Capital F, small f.
In If statement, why you putting condition in
between " " ? It becomes a string not condition.
if(0<overspeed&overspeed<=5) is correct way,
But not if("0<overspeed&overspeed<=5")

cin>>overspeed; //take input before output... If it is variable.
cout<<overspeed<<endl; //remove "" and it is not end1, it is endl means end line.
cin>>fine;
cout<<fine<<endl;
if (0<overspeed&overspeed<=5)
Same for all others..