Explanation:
the line goes through e.g. (0, -3) and (-2, 1).
the slope of the line is the defined by
x changes by +2 (from -2 to 0).
y changes by -4 (from 1 to -3).
so, the slope is -4/+2 = -2.
and the y-intercept (the y value when x = 0) is -3.
the line equation is then
y = -2x - 3
and we see in the graphic that all values smaller than the line values are covered (and the line is dotted, so it is not included).
so, the inequality is
y < -2x - 3