Let the length of rectangle = 5x and breadth of triangle = 3x

According to the question,

5x-3x=8  => 2x=8

x=4

Length = 5x =\( \Large 5\times 4 \) = 20 m

Breadth=3x = \( \Large 3\times 4 \) =12 m

Required area = \( \Large Length\times Breadth \)

= \( \Large 20\times 12 \)=240 sq m