You go to see family in another city. So far you have gone 120 miles. The total trip is 360 miles. What fraction of the total trip, in lowest terms, has been traveled?
So you've gone 120 miles, and the total trip is 360 miles, so you've gone 120/360 of the trip.
You can simplify this fraction by dividing the top and the bottom of the fraction by common factors.
I can see that 10 is a common factor, so:
120/360 = (120/10)/(360/10) = 12/36
I can see that 12 is a common factor, so:
12/36 = (12/12)/(36/12) = 1/3