15=6-3/4p+9/

the parenthesis mean absolute value

2 answers

15 = 6 - 3│4p+9│
3│4p+9│ = -9
│4p+9│ = -3

This is a contradiction of the absolute value definition, so there is no solution
If you meant to write

15 = 6 -3|4p+9|,
that can be rewritten
9 = -3|4p+9|
or
-3 = |4p+9|
which is not possible, since an absolute value cannot be negative.

There is no solution.