So, Tara, remember that absolute value is distance from 0, and distance is measured positively. That's why 12 and -12 both have an equal absolute value, because they are the same distance from 0.
So, the inside could equal 13 or -13, because both have an absolute value of 13.
7 - 6n = 13
-6n = 6
n = -1
7 - 6n = -13
-6n = -20
n = 20/6 = 3 1/3
So, n = -1 or n = 3 1/3