In a particular redox reaction, MnO2 is oxidized to MnO4– and Ag is reduced to Ag. Complete and balance the equation for this reaction in acidic solution. Phases are optional.

Answer 1

You didn't put a + charge on one of the Ag. It has to be on the left side
2H2O + MnO2 ==> MnO4^- + 3e + 4H^+
Ag^+ + e ==> Ag^+

Those are the two BALANCED half reactions. Multiply equation 1 by 1 and equation 2 by 3 and add them.