Answer:
15%
Explanation:
Since it is increasing from 13 to 15, the difference is 2
so you now
have to divide 2 by 13
because 13 is the original friend amount.
2 divided by 13 is equal to 0.153846153846153846153846153846
since the units are percent
it should techincally turn into
15.3846153846153846153846153846
but since you are rounding to the nearest percent
it would be 15%