So i failed my math test because i wasnt at school for a week and didn't know here is the question: 5^-8 x 5^4

When multiplying two powers with the same base (which is 5 in this case) you can simply add the exponents. - 8 + 4 = - 4. The answer is

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.