If 6 $\times$ 4 = 12, 7 $\times$ 5 = 20, 5 $\times$ 8 = 21, then 5 $\times$ 7 = ?

Correct Answer: (B) 18

The pattern follows the rule $(a - 2)$$\times$ (b - 1): for $6$$\times$ 4, $(6 - 2)$$\times$ (4 - 1) = 4 $\times$ 3 = 12; for $7$$\times$ 5, $(7 - 2)$$\times$ (5 - 1) = 5 $\times$ 4 = 20; for $5$$\times$ 8, $(5 - 2)$$\times$ (8 - 1) = 3 $\times$ 7 = 21. Applying this rule to $5$$\times$ 7, we get $(5 - 2)$$\times$ (7 - 1) = 3 $\times$ 6 = 18.