The number of seats sold cannot be negative, so you have
... x ≥ 0, y ≥ 0
The limits on numbers of seats must be observed, so you have
... y ≤ 2000
... x + y ≤ 3000
And the revenue constraint must be met:
... 35x + 50y ≥ 90,000
Together, these inequalties are ...
{x ≥ 0, y ≥ 0, y ≤ 2000, x + y ≤ 3000, 35x + 50y ≥ 90,000}