Answer:
5 gg
Explanation:
Let us treat the number of gigabytes of data she can use (at max) per month as x.
We can say that
will always be deducted from her and $5x per month for the extra data she uses.
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As she can only buy a fixed number of data, which cannot be a decimal, let us take the number directly below 5.1 - which is 5 - as the answer.
Caroline can use up to 5gg of data