check the picture below.
since we know is a rectangle, then we can simply find a width and a length, say hmmm CD and CB and get their product, recall that the area of a rectangle is width*length.
[tex] \bf ~~~~~~~~~~~~\textit{distance between 2 points}
\\\\
C(\stackrel{x_1}{-4}~,~\stackrel{y_1}{-3})\qquad
D(\stackrel{x_2}{-7}~,~\stackrel{y_2}{1})\qquad \qquad
d = \sqrt{( x_2- x_1)^2 + ( y_2- y_1)^2}
\\\\\\
CD=\sqrt{[-7-(-4)]^2+[1-(-3)]^2}\implies CD=\sqrt{(-7+4)^2+(1+3)^2}
\\\\\\
CD=\sqrt{(-3)^2+4^2}\implies CD=\sqrt{9+16}\implies \boxed{CD=5}\\\\
------------------------------- [/tex]
[tex] \bf C(\stackrel{x_1}{-4}~,~\stackrel{y_1}{-3})\qquad
B(\stackrel{x_2}{4}~,~\stackrel{y_2}{3})
\\\\\\
CB=\sqrt{[4-(-4)]^2+[3-(-3)]^2}\implies CB=\sqrt{(4+4)^2+(3+3)^2}
\\\\\\
CB=\sqrt{8^2+6^2}\implies CB=\sqrt{64+36}\implies \boxed{CB=10}\\\\
-------------------------------\\\\
\stackrel{\textit{area of rectangle}}{CD\cdot CB}\implies 50 [/tex]
