To add these fractions together, we need to find a common denominator. In this case, the least common denominator is 3600.

So, we need to rewrite each fraction with a denominator of 3600:

3/56 = 192.8571/3600
3/72 = 150/3600
3/600 = 18/3600

Now, we can add them together:

192.8571/3600 + 150/3600 + 18/3600 = 360/3600

Therefore, the sum of 3/56 + 3/72 + 3/600 is 360/3600, which simplifies to 1/10.