Some Basic Concepts Of Chemistry

If a substance '\(A\)' dissolves in solution of a mixture of '\(B\)' and '\(C\)' with their respective number of moles as \(\mathrm{n}_{\mathrm{A}}, \mathrm{n}_{\mathrm{B}}\) and \(\mathrm{n}_{\mathrm{C}_3}\). Mole fraction of \(\mathrm{C}\) in the solution is