5 mph to get that answer you use the speed equation
speed(mph)=distance(in miles)/time(in hours)
2.5
------ = 5 mph
.5
Okay so, f(x) is another way of writing y.
If the problem were to give you an x value you would put it in the x spot.
For example:
f(x) = 1/2x - 7
is the same thing as y = 1/2x - 7
If the problem were to say: "Solve for y, if x = 2" your problem would look like this
f(2) = 1/2(2) + 7
Now, multiply 1/2 by 2, and you get 1. Now the equation is:
f(2) = 1 + 7
So add 1 and 7 = 8
so that would be f(2) = 8
And your final answer would be y = 8
<em><u>I hope this helps and makes a little sense!</u></em>
To find the length of the arc given the central angle, multiply (the fraction of the angle of the full circle, 360°, that the central angle, 120°, makes up)*(the total circumference of the circle). You're basically finding the fraction of the circumference that is covered by the central angle, if that makes any sense.
So the central angle makes up

the entire circle. You are given that the circumference of the circle is 18. Multiply the fraction of the full circle that the central angle makes up (

) by the circumference of the circle:
The length of your arc is 6.
Let me know if you're confused b/c my explanation isn't the greatest :) I'll try to explain it better if you don't understand.