Answer
The distance between the second and fourth points is $2\sqrt{10}$ units.
Work Step by Step
RECALL:
The distance $d$ between the points $(x_1, y_1)$ and $(x_2, y_2)$ is given by the formula
$d=\sqrt{(x_1-x_2)^2+(y_1-y_2)^2}$
Use the formula above to obtain:
$d=\sqrt{(1-3)^2+(-3-3)^2}
\\d=\sqrt{(-2)^2+(-6)^2}
\\d=\sqrt{4+36}
\\d=\sqrt{40}
\\d=\sqrt{4(10)}
\\d=2\sqrt{10}$