Cu3P+Cr2O7−2+H+1→Cu+2+H3PO4+Cr+3  the coefficient for Cu3P in balanced equation is

Step1:Reduction half- cell reaction:Cr2O72−→Cr3+ Step2:Balancing species undergoingCr2O72−→2Cr3+ Step3:Oxidation half- cell reaction:P3-→PO43- Adding reduction half-cell and Oxidation half-cell reactions:Cr2O72-+P3-→2Cr3++PO43- Step4:Multiplying change in Oxidation half-cell number in reduction half-cell reaction toOxidation half reaction and vice versaCr2O72-+3P3-→2Cr3++3PO43- Step5:Balancing the Oxygen using  H2O and hydrogen using H+ions5Cr2O72−+6Cu3P+22H+→10Cr3++6PO4-3+18Cu2++11H2O