First look at √(60+n). The first positive value of n that will make 60+n into a perfect square is 4, and √64 = 8.
Look at √(2n+28). If n = 1, 2, 3, (2n+28) = 30, 32, 34, whose square roots are all irrational. But if n = 4, we get √(2*4+28) = √36 = 6, which is rational.