Question 953174
12-x_<2x+6_<21-x
Inequality showing how three different but related expressions are ordered.


Plain text:  12-x<=2x+6<=21-x

Rendered:  {{{12-x<=2x+6<=21-x}}}


Add x to all members,
Add {{{-6}}} to all members;
Multiply all members by {{{1/3}}}.


The variable is isolated; simplify.
Done.