Given system of equation more than 2 solutions. Hence system of equation has infinite many solution.

$$ \therefore $$ $$\Delta $$ = $$\Delta $$₁ = $$\Delta $$₂ = $$\Delta $$₃ = 0

$$\Delta $$ = $$\left| {\matrix{ 1 & 1 & 1 \cr 1 & 2 & 3 \cr 3 & 2 & \lambda \cr } } \right|$$ = 0

$$ \Rightarrow $$ 1(2λ – 6) – 1(λ – 9) + 1(– 4) = 0

$$ \Rightarrow $$ 2λ – 6 – λ + 9 – 4 = 0

$$ \Rightarrow $$ λ = 1

$$\Delta $$₁ = $$\left| {\matrix{ 6 & 1 & 1 \cr {10} & 2 & 3 \cr \mu & 2 & \lambda \cr } } \right|$$ = 0
6(2λ – 6) – 1(10λ – 3μ) + 1(20 – 2μ) = 0

$$ \Rightarrow $$ 12λ – 36 – 10λ + 3μ + 20 – 2μ = 0

$$ \Rightarrow $$ 2λ + μ = 16

$$ \Rightarrow $$ 2 + μ = 16

$$ \Rightarrow $$ $$\mu $$ = 14

$$ \therefore $$ $$\mu $$ - $$\lambda $$² = 14 - 1 = 13