in a Rectangle
distance AE= 14 m , DE=4 m, CE=12 M
find BE=X=?
Let $\displaystyle EM\perp AD, \ EN\perp DC, \ EP\perp BC, \ EQ\perp AB$
$\displaystyle EM=a, \ EN=b, \ EP=c, \ EQ=d$
Then,
$\displaystyle a^2+b^2=16$ (1)
$\displaystyle b^2+c^2=144$ (2)
$\displaystyle c^2+d^2=x^2$ (3)
$\displaystyle d^2+a^2=196$ (4)
(1)+(3)$\displaystyle \Rightarrow a^2+b^2+c^2+d^2=x^2+16$
(2)+(4)$\displaystyle \Rightarrow a^2+b^2+c^2+d^2=340$
$\displaystyle \Rightarrow x^2+16=340\Rightarrow x^2=324\Rightarrow x=18$