ZOO Revenue from single-day ticket sales at a local zoo can be modeled by the function y=-x + 25x +80, and revenue from season pass sales can be modeled by the function y=-4x+ 200. In both functions, x represents the number months, and y represents the total amount in thousands of dollars. Solve a system of equations algebraically to find the first month when the revenue from single-day ticket sales is equal to the revenue from season pass sales.