Answer
84
Work Step by Step
*This question is listed as 57. in the book, but should be listed as 58.*
If she has 300% of the Facebook friends now that she had one month ago, this means that she now has 3 times as many friends as she had last month. Therefore, she now has $3\times28=84$ friends.
300%$=300\div100=3$
$28\times3=84$ friends