The answer is four. It's like asking to give the least common denominator
16...................................
Pick a number: 5
Add 7: 5+7=12
Triple the result: 12*12*12=1728
Add 9= 1728+9=1737
Divide by 3 = 1737/3=579
Subtract original number = 579-5=574
Now pick a different number a do the same process
Hope that helps
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