Answer: 55 brushes.
Explanation:
Let x represents the number of art brushes Monique has.
Then, Number of brushes Chelsea has = 11x .
If they have 60 art brushes altogether, the we have the following equation :-

Divide both sides by 12 , we get

Then, Number of brushes Monique has = 5
Number of brushes Chelsea has = 11(5)=55