Answer
Consistent
All real numbers in $x$ and $y$.
Work Step by Step
$3x - y = 7$ $(1)$
$9x -3y=21$ $(2)$
Multiply Equation $(1)$ by 3
$9x - 3y=21$ $(1)$
$9x -3y=21$ $(2)$
When you subtract the two equations, the equation is always true for any real value of $x$ and $y$; therefore the system is consistent.