A third are spotted so that would mean 2/3 are not spotted so if you take 1200 divide it by 3 and then multiply it by 2 you get 800 which is your answer
So convert to improper fracitons (improper=x/y where x>y and the current one is mixed where it is in t s/f form) so
40 and 4/5=(40 times 5)/5 and 4/5=200/5 and 4/5=204/5
50 and 7/8=(50 times 8)/8 and 7/8=400/8 and 7/8=407/8
area=legnth times width
legnth =407/8
width=204/5
multiply 407/8 and 204/5
407/8 times 204/5=(407 times 204)/(8 times 5)=83028/40=2075.7 square feet
the answer is 2075.7 ft^2 of seed