Answer: Bea's uncle is 25 years old.
Explanation:
Given the equation
, we can say that the variable "x" represents the age of Bea's uncle. Then to find his age, we need to solve for "x":
We must add 15 to both sides of the equation:

Now we need to divide both sides of the equation by 3:

Therefore, we can conclude that Bea's uncle is 25 years old.