Make a drawing with point A being the initial position on the boat, B somewhere to the right indicating the position of the boat when it is over the fish and C the position of the fish directly below point B
This gives you a right triangle ABC with angle a = 25 degrees AC is the hypotenuse which is 150 yds.
You need to find AB so
Cosine 25 = AB/AC
AB= Cosine 25 X 150 = 135.94 yds = 136 yds rounding to nearest yard