Puzzle ZWSM 

Workings

Hint
Look at the rows.

Answer
4.

For each row, the left minus the right gives a number. The numbers for the rows are then multiplied together. In the left figure 7 - 3 = 4 and 4 - 1 = 3. 4 * 3 = 12. In the right figure 6 - 2 = 4 and 8 - 7 = 1. 4 * 1 = 4.