Which is the angle of depression from the boat to the submarine?

If the slope of the angle from the vertex is positive, then it is an angle of elevation.

If the slope of the angle from the vertex is negative, then it is an angle of depression.

The angle of elevation is congruent to the angle of depression because they are alternate interior angles

in the picture

∠ 1 is the angle of elevation from submarine to the boat

∠2 is the angle of depression from boat to submarine

∠3 is the angle of elevation from boat to the lighthouse

∠4.is the angle of depression from the lighthouse to the boat

therefore

the answer is

∠2 is the angle of depression from boat to submarine

set each factor equal to 0

4x-3 = 0

2x-1 = 0

solve for x.

4x-3=0

4x=3

x= 3/4

solve for x. 

2x-1= 0

2x= 1

x= 1/2

eventually after a few more steps, your answer should be 1/2 is less than or equal to x and 3/4 is greater than or equal to x