the answer is fill its tanks with air so it floats to the top, but I will solve for the distance since I am nice
so we do
decent means negative
cimb=positive
add
decends 45 and 1/2
-45 and 1/2
climbs 39
+39
decedns 18 and 3/4
-18 and 3/4
add
-45 and 1/2+39-18 and 3/4
add
convert 1/2 to 2/4
gropu negatives
-45 and 2/4-18 and 3/4+39
add
-63 and 5/4+39
-64 and 1/4+39
-25 and 1/4
that is how far dow the submarine is
so the submarine needs to gu 25 and 1/4 ft up to reach the csurface
