Ettenheim village is considering building a town swimming pool. The annual facility cost would be $200,000. Staff salaries for the pool, which would only be open during the summer would be $75,000. Other fixed cost would be $20,000 a year. There are other expenses of $50 per person per season.

Marketing studies suggest that the village residents would be willing to spend $150 a year for an individual membership and $300 for family membership. On average families in the village have 3 people. How many members will have to join each year to make the pool cover its cost. Assume that 75% of the memberships are family memberships.

members(.75*300+ .25*150)=200K+ 95k + (3*.75member + 1*.25members)50

That is the income=cost equation.
solve formembers.