Question

how to balance a chemical equation i want it with perfect explanation

Answer 1

A balanced chemical equation is as  when the number of atoms  on each side of the equation is the equal. for example  if you have 12 hydrogens on the left hand side of the equation, you must have 12 hydrogens on the right hand side, if there are 4 oxygens on the left, there must  be 4 oxygens on the right, and so on. This is because of the law of conservation of mass - you can't create or destroy atoms during a chemical reaction. But you can't just add atoms.To balance that element, multiply the chemical species on the side which doesn't have enough atoms of that type by the number required to bring it up to the same as the other side.         

                                
                                     a. If the selected element is already balanced, put the SAME letter coefficient at its blank lines. b. If the element is not balanced, put first the letter coefficient at the side with the GREATER number of atoms for that element, and balance the other side in terms of the same letter coefficient. For example, the letter coefficient could be “a” and the coefficient for the other side could be “2a”. c. Repeat step 1, if needed, with another letter coefficient.                                

Answer 2

A balanced equation means   for every element, there is the same number of atoms on both sides of the reaction .
for example

H2O + PO4 + C8 ---------> H8O4 + P3O12 + C16

for example, you can treat PO4 as a compound and balance the whole compound at once, instead of trying to do each element separately, same with H2O.The law of conservation of mass states that no atoms can be created or destroyed in a chemical reaction, so the number of atoms that are present in the reactants has to balance the number of atoms that are present in the products.