KBr + AgNO3 → KNO3 + AgBr
Zn + 2HCI → H₂ + ZnCl₂
MgCO3 → MgO + CO₂
2Fe(OH)3 → Fe₂O3 + 3H₂O
Na₂CO3 + Ca(OH)2 → CaCO3 + 2NaOH AgNO3 + HCI → AgCl + HNO3
Out of the chemical equations above, how many is (are) considered as a double replacement reaction?