At a 4 hour race, a runner ran 1/4 the race in the 1st hour, 1/5 the race in the 2nd hour, 1/3 in the 3rd hour. If a total of 120 miles was run, how many miles were run in the 4th hour?

I get 1/4 =30  take that from 120 is 90 and 1/2 of that is 45, so add 45 to the 30 already run is 75 and take that from 120 is 45 and 1/3 of that is 15 and added to 75 already run is 90 and take that from 120 leaves 30 for last hour. So now I'm not sure who is right but are close is answer