Let the equation have coefficients as follows:
A C5H11NH2+B O2→C CO2+D H2O+E NO2
Balancing the number of atoms of each element on both sides, we get
5A = C
11A + 2A = 2D
13A = 2D
A = E
2B = 2C + 2E + D
C5H11NH2 has the largest number of atoms.
Hence let A = E = 1
Then, C = 5
2D = 13 ⇒ D = 132
2B=10+2+132
4B = 20 + 4 + 13 = 37
⇒B=374
Therefore, C5H11NH2+(374)O2→5CO2+(132)H2O+NO2
Multiplying by 4, we get
4C5H11NH2+37O2→20CO2+26H2O+4NO2