## Algebra 2 (1st Edition)

$3500$ lower-level and $6300$ upper-level seats were sold.
Let $x$ be the number of lower-level seats sold. Then the number of upper-level seats sold is $9800-x.$ Then our equation is: $35x+(9800-x)25=280000\\35x+245000-25x=280000\\10x=35000\\x=3500$ Thus $3500$ lower-level and $6300$ upper-level seats were sold.