Respuesta :

akephd
Rewrite as
11+(7x)-x=-21
11+6x=-21
6x=-32
X= -32/6 = -16/3

Check:
11+(-16/3*7)+16/3=
11-112/3+16/3=
11-96/3=
11-32=
-21 it works

So...?= -16/3