Answer:
131 minutes, an = 15 + (n - 1)(4)
Explanation:
each time she is increasing by 4 minutes
we can write this equation like this since we have the difference and the first part:
an = 15 + (n - 1)(4)
note
"an" (or ace of n)'s n is in subscript and is written just like a superscript but on the bottom
we can plug in this equation to find ace of 30 (a30)
15 + (30 - 1)(4)
15 + 29*4
116 + 15
a30 = 131