From the given value of B = 6 and D = 30 AB + C = D ⇒ 6A + C = 30 ...(i) From value of B = 8 and D = 30 AB + C = D ⇒ 8A + C = 36 ...(ii) From Eqs. (i) and (ii), we get 2A = 6 ⇒ A = 3 Put A = 3 in Eq. (i), 18 + C = 30 and C = 12 ∴ A = 3 and C = 12