Question

How do I figure out how to balance 1 mole of carbonic acid with 1 mole potassium hydroxide? And balance a chemical reaction of sodium bicarbionate with hydrochloride acid?

Answer 1

Both of them are balanced by inspection which, in real terms, means trial and error.
H2CO3 + 2KOH ==> K2CO3 + 2H2O
NaHCO3 + HCl ==> H2O + CO2 + NaCl