The variable coefficients a, b, c and d are considered for balancing the chemical equation.
The relation we get by balancing K in the following equation is:
a=c
a=3c
a=2c
2a=c
a=2c
Number of K atoms on product sideNumber of K atoms on reactant sidea∗1C∗2
The number of K atoms on product and reactant should be equal.
Implies, a=2c.