so what i would do is take 3/5 and multiply is all by 3 so you end up with 9/15.
Now after you have done that do this, 9/15+ 4/15. Add 9/15 and 4/15 together which has a sum of 13/15 now add 11 + 6 which is 17 then add in the 13/15 and you get the answer of 17 13/15