Hey there!
The correct answer would be~
The diver is now swimming at <u> -7 meters.</u>
Here's how:
If the diver is already swimming at negative 10, going deeper would <em>add </em>to that.
(-10) + (-3) = -13
So at this point, he is at -13 meters. However, it says he rises <em>6 meters. </em>
So if he rises, we need to subtract.
13 - 6 = 7
Therefore he is now at <em>-7 meters.</em>
Hope this helps!
~Fluerie