Answer:
l( longer side ) = 12cm 
 
S (shorter side) =9cm 
 
D's( distance between the shorter side). ( It is also the height. I hope you got the clue…) 
 
Anyway, 
 
Area=9X8=72cm^2 
 
Distance of the longer sides is 
 
Area/the length of the longer side 
 
72/12=6cm… 
 
Distance between the longer sides is 6cm 
 
Hope this helps…