Let X be the age of Cooper. So Dante is X*2 years old and Maria is X*2 + 1 year old.
The sum of Cooper’s, Dante’s, and Maria’s ages is X + (X*2) + (X*2 + 1) = 31.
Combining like terms, we get X*5 + 1 = 31.
Subtracting one from both sides, we get X*5 = 30.
Dividing both sides by 5, we get X = 6 years old.
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