To determine viable solutions for the inequality 7x + 4y ≥ 400, we need to consider the constraints that are relevant to the context of the problem.
In this case, since we are dealing with the cost of entry tickets for a local fair, it is reasonable to assume that the number of adults (x) and children (y) attending the fair cannot be negative or fractional values. Additionally, we usually don't consider a negative number of attendees in real-world scenarios.
Therefore, the correct constraint to determine viable solutions would be:
A viable solution will have only positive whole numbers.
This means that the number of adults and children attending the fair must be positive integers, and the solution must satisfy these requirements along with the given inequality.