Answer:
The mystery divisor is 18
Step-by-step explanation:
In the beginning, I found it by simply dividing the dividend by the quotient which gave me the divisor of 18. You can start the division equation again and add in the divisor 18 and it'll give you the exact answer.
Another way you'll know it's correct, is by dividing the dividend by that divisor and it'll give you the quotient 225 just like in the image.