The math get fairly complicated due to RH's, but, keeping it simple:
5 Common/pack-43 common/set
So, the probability on that is as such:
The odds of pulling a Pansage 7/114:
The probability of the first common NOT being Pansage: 42/43
The probability of the second common NOT being Pansage: 41/42....and so on:
42/43 = 97.7%
41/42 = 97.6%
40/41 = 97.6%
39/40 = 97.5%
38/39 = 97.4%
97.7%*97.7%*97.6%*97.5%*97.4%= 88.4% you DO NOT pull Pansage.
100-88.4= 11.6% chance you DO pull Pansage. So, there is an 11.6% chance to pull any common. In all reality, its a bit different due to RH's, but that is a good starting point.
Use the same logic for Uncommon's and Rares.