If a kilogram of wheat flower is $6.what is the cost of 400 grams of flour

1 kg = 1000 g

You can set it up as a proportion:
(1000g below is the measure of 1 kg.)
1000g/$6 = 400g/x
Find x.
Cross multiply:
x=(400*6)/1000= 2400/1000
x=2.4
It costs $2.40 to buy 400g of flour.

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.

I’m confused as to what you are asking 66 2/3 percentage wise