You have the following equation:
|2n + 5| = 11
In order to solve the previoues equation for n, you take into account that an equation with an absolute value has two solutions. In this case you have:
2n + 5 = 11
2n + 5 = - 11
That is, the equation must be solved for both cases.
For the first equation you have:
2n + 5 = 11 you add 5 both sides
2n = 11 - 5
2n = 6 divide by 2 both sides
n = 6/2
n = 3
For the second equation you have:
2n + 5 = -11 add 5 both sides
2n = -11 - 5
2n = -16 divide by 2 both sides
n = -16/2
n = -8
Hence, the solutions to the given equation are:
n = {3,-8}