I explained this in my comment on your previous question... Let's take the first fraction, 2/7. So we can say that the mid-point of 7 is 3.5... So 3.5/7 is 50%. Is 2/7 greater than the 50% value we established or no? It's not, so we round down to 0. On the other one, 7/9, is it greater than the 50% value? Yes so we round up to 1. (5+0) which is the first fraction - (2+1) which is the second fraction, gives you an estimation of 2.
