In a lottery, 5 balls are selected from a bin of twenty balls numbered 1 through 20. (The order doesn't matter.) Professor Luckless always guesses a 5-ball combination that includes her lucky number 7, and does not include her unlucky number 13. How many different days can she play the lottery without repeating a 5-ball guess?

Since opening night, attendance at play a has increased steadily, while attendance at play b first rose and then fell. equations modeling the daily attendance y at each play are shown below, where x is the number of days since opening night. on what day(s) was the attendance the same at both plays? what was the attendance? play a: y = 8x + 191 play b: y = -x^2 + 26x + 126