An herbalist has 20 oz of herbs costing $4 per ounce. How many ounces of herbs costing $2 per ounce should be mixed with these 20 oz of herbs to produce a mixture costing $2.80 per ounce?

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.

3you can not round up to four, as there was not a full payment for the fourth night, so uou would round down to 3