Which equation shows conservation of m and charge?

Look at the charges of Cu and Ag. On the left side, Cu is a 0 charge, since it is in it's elemental state. It gets oxidized and becomes a +2 charge, so there was a transfer of 2 electrons from reactants (left) to products (right). The Ag has a +1 charge originally, but there are two, so there is a total of +2 charge on the Ag. It gets reduced and becomes a 0 charge, because it is in it's elemental state, like Cu on the reactant side. Conservation of m and charge just means the equation is balances and that the number of electrons transferred from reactants to products equals the number of electrons transferred from products to reactants. In this case, 2 electrons are transferred to the product side, and 2 electrons are transferred to the reactant side, and the equation is balanced, thus showing conservation of m and change.