7 meters
This is just a matter of reading the problem and constructing an expression for it. So let's start.
"A scuba diver descends to a depth of 30 meters below sea level"
d = 30
"and then rises 23 meters" Since rising is the opposite of descending, will use the opposite sign. Giving:
d = 30 - 23
Solve for d
d = 30 - 23 = 7
So the diver is 7 meters below the surface when he studies the fish. Assuming the fish are at the same depth as the diver, then the fish are also 7 meters below the surface.
