Answer:
Length = 200 m
Breadth = 175 m
Explanation:
Perimeter of the rectangular field = Total cost ÷ rate per metre
 = 12000 ÷ 16
 = 750 m
Length : breadth = 8 : 7
Length = 8x
Breadth = 7x
Perimeter = 750
2*(length + breadth) = 750
2*(8x + 7x) = 750
2* 15x = 750
 30x = 750
 x = 750/30
x = 25 
Length = 8x = 8*25 = 200 m
Breadth = 7*25 = 175 m