What is the center of a pipe with a 6 7/8" outside diameter?

X+y=-4 x-y=2 use elimination with adding and subtraction

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.

3x = 729 solve for x plz . it's urgent. will mark