Each week, you drive 150 miles. your car gets 25 miles to the gallon, and gas prices are $3 per gallon. how much gas money will you spend on gas each week? $41.67

150/25 = 6
6 * 3 = 18 <== gas for the week

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.