Can you explain where does the number 3 come from in NH4 + PO4 → (NH4)3 PO4 = AMMONIUM PHOSPHATE, and explain how you balance this equation
(NH4)3PO4 is ammonium phosphate.
This compoundf is comosed of two ions; i.e., the ammonium [(NH4)^+] ion and the phosphate [(PO4)^3-] ion. Note that the ammonium ion has a +1 charge and the phosphate ion has a 3- charge. All compounds are zero charged so the charge of ammonium phosphate must be zero. Hence, there must be three +1 NH4^+ ions to balance the one 3- charge on the phosphate ion; therefore, the formula is (NH4)3PO4.
To balance I must make a few changes since the question has no charges and isn't right. 3[NH4]^+ + [PO4]^3- → (NH4)3PO4 = AMMONIUM PHOSPHATE