To add and subtract fractions, we need to have a common denominator.

The common denominator for 30, 20, and 60 is 60.

2 7/30 = 2 + 7/30 = 60/30 + 7/30 = 67/30

3 9/20 = 3 + 9/20 = 60/20 + 9/20 = 69/20

4 59/60 = 4 + 59/60 = 240/60 + 59/60 = 299/60

Now, we can add and subtract:

67/30 + 69/20 - 299/60

To add and subtract, we need a common denominator of 60:

67/30 2/2 = 134/60
69/20 3/3 = 207/60

Now we have:

134/60 + 207/60 - 299/60 = 42/60 = 7/10

Therefore, 2 7/30 + 3 9/20 - 4 59/60 = 7/10.