find the two non linear equations with two variables (r1,r2)

At equilibrium, the final concentrations of the species must satisfy the equilibrium constants of each reaction (a parameter that depends on the particular reaction and the temperature of the system): K1=ca2cbccK1ca2cbcc=0K2=cacdccK2cacdcc=0 Using a mole balance for each species and the stoichiometry of the reactions, we can express these final concentrations in terms of the initial concentrations of each species and the extent of each of the reactions (r1 and r2): ca=ca02r1r2cb=cb0r1cc=cc0+r1+r2cd=cd0r2 By substituting these expressions in equations 7 we end up with two non-linear equations with two variables (r1 and r2)