For infinite number of solutions, all determinants D,D1,D2andD3 must be zero and planes represented by these equations should not be parallel. So, we have,
D=∣11112313λ∣=0⇒λ=5
D1=∣25μ12313λ∣=0
D2=∣11125μ13λ∣=0
And D3=∣11112325μ∣=0⇒μ=8