Explanation:
I assume this means that both purchase one item every day.
so, their number of purchases are the same (x).
80 - 4.5x >= 60 - 2.5x
20 - 4.5x >= -2.5x
20 >= 2x
10 >= x
our
x <= 10
after 10 purchased drinks their balances will be equal.
before that, Ashley's card balance will be greater than Aaron's.
after that, Aaron's card balance will be greater than Ashley's.
so, for up to 10 purchased drinks Ashley's card balance will be greater or equal to Aaron's.