Х-15,5+8х-(13х+16,5)=12х
x-15.5+8x-(13x+16.5)=12x
x-15.5+8x-13x-16.5=12x
x+8x-13x-12x=15.5+16.5
-4x=32
x=32/(-4)
x=-8
Ответ:-8