Question

Write a balanced overall reaction from these unbalanced half-reactions.

Sn->Sn2+
Ag+->Ag
Balanced overall equation

I got Sn+2Ag+->Sn+2Ag, but its wrong.

Answer 1

I think you just made a a couple of typos. You left no space between Sn+2Ag and you omitted the 2Ag on the right.
Sn + 2Ag ==> An^2+ + 2Ag