Answer
empty, inconsistent, parallel
Work Step by Step
When solving
$12x-21y=24$
$4x-7y=7$
by the addition method, we obtain $0=3$, so the solution set is empty. The linear system is a/an inconsistent system. If you attempt to solve such a system by graphing, you will obtain two lines that are parallel.
This is mentioned on pages 522-23.
