Answer:
He went down 9 feet, aka -9.
Step-by-step explanation:If he is 6 feet below the surface then he is in the negatives, -6, all you need to do is add the numbers to see how much he went down, you need to reach the original number, like -6(current) plus +6(the opposite of his negative to reach the normal surface ground), plus 3( where he was before) equals 9.
