Answer
The steeper line is the one whose slope is $-3$.
This is because steepness does not take into account the sign of the slope. Instead, it is based purely on the vertical rise divided by the horizontal run.
Work Step by Step
The steeper slope is the one with the higher absolute value.
$|-3| = 3
\\|2|=2$
Thus, the line with a slope of $-3$ is steeper than the line with a slope of $2$.
This is because steepness does not take into account the sign of the slope. It is based purely on the vertical rise divided by the horizontal run.