Hello!
your answer is: B. n + 25 = 61
If megan had 25 numbers, and both Megan's and Abby's total numbers add up to 61, then n is the amount of numbers you need to add to 25 to get 61.
n + 25 = 61
36 + 25 = 61
therefore n = 36
I hope this helps, and have a nice day!