Answer: The number is 15.
Step-by-step explanation: We are given a certain number we don't know about. Since it's value is unknown it is a variable. We'll call this variable "x". That number, x, is divided by 3, and then 3 was added to x to make 8. So then if x = 15, then dividing it by 3 would make 5, and adding 3 to that would make 8.
Another way to solve this, or check your work, is to work the problem out in reverse. Starting with the number 8, subtract 3 and then multiply that number by 3. This will give you the number 15. Which shows that the answer is correct.
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Thus the number is 15. Hope this helps, and have a great day!