Explanation:

C2H4 + 02 -> CO2 + H2O

C,H and O atoms Are Not Equal In RHS Than LHS

No. of C Atoms in LHS = 2

No. of H atoms " " = 4

No. of O atoms in LHS = 2

For Balancing Multiplying 3 in O2 in LHS

& Multiplying 2 to Both CO2 & 2H2

So That All The Atoms In LHS & RHS Will Be Same

& There We Can Say Mass is Conserved

C2H4 + 3O2 -> 2CO2 + 2H2O

Hence The Equation is Balanced