Add $3$ to both sides.
$−2x−3=3$
$\ \ \ \ \ \ \ +3\ \ +3$
$−2x=6$

Add $3$ to both sides.
$7+2x=4x−3$
$+3\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ +3$
$10+2x=4x$

Refer to part (b).