First, AgNO3. N is either -3 or a +5, in this case it’s a +5 since O is almost always a -2. So O3 is a total of -6, then added to N would make it a -1. So it’s NO3-, then Ag (silver) is a +1 or Ag+.

Second, Fe(HCO3)2, the only question you’ll see as I go thru it is Iron a +2 or a +3, because it is commonly one or the other. H is always a +1, C is either a -4 or +4, O is, again almost always a -2. Then with a little algebra…, C is +4, then O3 accounts for -6, now we’re at -2…, H is a +1, so now we’re at -1. Then watch the parentheses of 2 and the whole thing is -1 x 2 = -2. So the Fe (iron) here is a +2 (Fe+2). Likewise, HCO3 is a -1 (HCO3-)