Which phrase describes an unknown or changeable quantity

Write a recursive sequence that represents the sequence defined by the following explicit formula:

For each proportion find the unknown number x 1/5/8=×/15

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