We are given that,

We need to find the value of a – 2b.

We know by the property of matrices,

This implies,

a₁₁ = b₁₁, a₁₂ = b₁₂, a₂₁ = b₂₁ and a₂₂ = b₂₂

Therefore,

a + 4 = 2a + 2 …(i)

3b = b + 2 …(ii)

8 = 8

-6 = a – 8b …(iii)

We have the equations (i), (ii) and (iii).

From equation (i),

a + 4 = 2a + 2

⇒ 2a – a = 4 – 2

⇒ a = 2

From equation (ii),

3b = b + 2

⇒ 3b – b = 2

⇒ 2b = 2

⇒ b = 1

We have a = 2 and b = 1.

Substituting the values of a and b in

a – 2b = 2 – 2(1)

⇒ a – 2b = 2 – 2

⇒ a – 2b = 0

Thus, the value of a – 2b is 0.