I'm trying to perform basic algebra with summations and I haven't been able to find any information on whether it is possible in Mathematica.
For instance, I took this rule about multiplying sums from the Mathematica website (picture below) and tried to recreate it with this code
The output never looked like the right hand side of the equation (the expanded form of the product of sums).
Is this possible to do in Mathematica? I'm new and appreciate any help!