You pick any number to begin then just follow the tiles. Use a different number for each trial...
Trial 1
Pick a number... 2
Add 3... 2+3=5
Multiply by 3... 5*3 = 15
Subtract 3... 15-3 = 12
Divide by 3... 12/3 = 4
Subtract the original number... 4-2 = 2
Continue with trial 2... Use 3 this time, then use 4
If you do it right you should start and end with the same number.