The answer to this mind teaser math picture puzzle is 9 as explained below the picture

The logic is follow Bottom Left Set Step 1 : First read numbers from right to Left so the full number becomes 846 Step 2 : Subtract this number from the number 648 reading left to right Step 3 : The number becomes 198 which is transferred to the second set on the right it is important to note that number 198 is starting from left to right.

Bottom Right Set Similarly Step : First read numbers from right to left so the full number becomes 891 Step 2 : Subtract this number from the number 198 reading left to right Step 3 : The number becomes 693 which is transferred to the top set

In the top set link in the case of bottom left set we observe that the next number is written from left to right similarly the number 693 obtained from bottom right set is written in the top set in the same manner and since the two numbers six and three are already given only one number is missing which is 9 that is our answer