Harry Potter theme song played by a pencil + math equation

x=-6/15. See Pitch Perfect Cup Song played by a pencil:

See Havana by Camila Cabello played by a pencil:

-14x – 17 = -14 + x + 4 -1
-14x – x = -14 + 4 – 1 + 17
-15x = 6
x = -6/15