Insert the missing number marked as ‘?’.

In each column, the product of the first two numbers divided by the third gives the bottom number: 18 × 12 ÷ 3 = 72 and 32 × 16 ÷ 4 = 128. For the middle column, 24 × 14 ÷ ? = 112, so ? = 336/112 = 3.