Answer:
At&t Stadium (Dallas cowboys) = 80,000 seats
CenturyLink Field (Seattle Seahawks) = 65,000 seats
Gillette Stadium (New England Patriots) = 68,800 seats
Explanation:
The three stadiums all together have a total of 213,800 seats
We'll call X the Gillette Stadium seats. We already had that the At&t stadium had X seats + 11,200 seats. And also we knew that the CenturyLink Field had X seats - 3,800 seats. The we can write the following equation,
X + (X + 11,200) + (X - 3,800) = 213,800 seats (the total of seats of the 3 stadiums together). We need to find the value for X, that represents the Gillette stadium seats
Then we can write X + X + 11,200 + X - 3,800 = 213,800 seats,
This is 3X + 11,200 - 3,800 = 213,800,
3X + 7,400 = 213,800,
3X = 213,800 - 7,400,
X = 206,400/3 seats
X = 68,800 seats
As At&t is X + 11,200 seats, then it accommodates 80,000 people
And as CenturyLink Field is X - 3,800, it accommodates 65,000 people