There are two practices of balancing a chemical equation. The first one is balancing by Inspection. Balancing by inspection is the most basic method used. It works best for simple problems. More complicated ones require experience. The second one is Balancing by Numerical Method. The most important parts of the numerical methotrexate, contrary to the inspection method, it gives the answer. If the reaction can be balanced, coefficients can be seen. If the reaction can't be balanced, it means that there are more unidentified than independent statements, or that statements are opposite. With inspection method, it won't prove that the equation can't be balanced.