So first, you should try to write an equation to fit the problem.
You know Alice already read 91 pages. That number won't be affected by the variable, d, the number of days. 91 is your constant that will be added to the part affected by your variable.
You also know Alice is reading 15 books everyday. That number will increase by 15 with every day that passes, so the expression 15d can be used to find how many books she has read since she has decided to continue the book.
You know p is the total number of pages she has read, so set p equal to the sum of the the number of books read every day + the constant (number of books she has already read):
p = 15d + 91
Now put values in for d to find p:
When d = 2, p = 15(2)+91 = 121
When d = 4, p = 15(4)+91 = 151
When d = 6, p = 15(6)+91 = 181
When d = 8, p = 15(8)+91 = 211
So your answers are:
121
151
181
211
