The average age of 3 girls is 17years 4 months The average age of 2 of them is 17 years 3 months
How old is the third girl.

please explain your answer.
Thank you​
This the correct question

Acompany manufactures three types of cabinets. it makes 110 cabinets each week. in the first week, the sum of the number of type-1 cabinets and twice the number of type-2 cabinets produced was 10 more than the number of type-3 cabinets produced. the next week, the number of type-1 cabinets produced was three times more than in the first week, no type-2 cabinets were produced, and the number of type-3 cabinets produced was the same as in the previous week.