Add $3$ to both sides.

$−3+2x=−x+6$
$+3\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ +3$
$2x=−x+9$

Add $x$ to both sides.

$2x=−x+9$
$+x\ \ \ \ +x$
$3x=9$

Divide both sides by $3$.

$\frac{3\textit{x}}{3}=\frac{9}{3}$

$x=3$

Substitute $3$ back into the original equation.
$−3+2(3)=−(3)+6$
$−3+6=−3+6$
$−3=−3$

It works!

Refer to part (a).

$x=1$

$x=−1.5$

Use the same method as parts (a), (b), and (c). Make sure to check your answer as shown in part (a).