What ls 6q+m-m; use m=8and q =3

First of all, I see  +m  and  -m  on the left side, and I realize that when you combine those, they make zero-m.  So you can ignore them completely,
and that means that the value of 'm' has no effect on the value of that
expression.  It doesn't matter whether 'm' is  2.509  or 'm' is  8  or 'm'
is 9 hundred trillion.  Either way, the expression has the same value.

The value is   6q = 6(3) = 18 .