Consider the following code:
In[263]:= Clear["Global`*"]
m = 2;
a = 1/20;
k = 0;
Solve[Sum[PDF[PoissonDistribution[p], i], {i, k, m}] == a, p]
During evaluation of In[263]:= Solve::nsmet: This system cannot be solved with the methods available to Solve.
Out[267]= Solve[E^-p + E^-p p + 1/2 E^-p p^2 == 1/20, p]
I've tried many ways but haven't succeed. So how to solve this equation?
