You’re going to break apart radical 28 into square root of 4 and square root of 7.
The square root of 4 is 2 so you add the 2 to the 3 and it equals 5 and since the square root of 7 can’t be simplified and it stays the same. So all you do is add 4 radical 7 and 5 radical 7 which equals 9 radical 7.
