the wording of this problem is difficult to follow without some supplemental image or greater detail in the description, but we determine that this is an obtuse triangle problem with sides of 125 feet and 240 feet and the angle between the side of length 240 and the hypotenuse of the triangles they form is 25 degrees

we call the top of the tower point 'T', the base of the tower point 'B', the point at the bottom of the hill, from which the angle of 25 degrees is measured, point 'M'

our obtuse triangle is then 'TBM' and we also define a point 'G' that is at ground level and colinear with points 'T' and 'B' such that 'MBG' forms a right triangle whose hypotenuse is 240 feet

we want to solve for angle BMG, the angle the side of the hill makes with the horizontal

since triangle MBG is a right triangle, once we solve for angle MBG, we know BMG since the sum of the angles in any triangle is 180 degrees... and we know that the supplement to angle MBG is angle MBT, therefore once we solve for angle MBT we can easily calculate the desired angle, BMG

let 'x' represent angle MTB, then by the law of sines, we can solve for angle MTB:

sin(x)/240 = sin(25)/125

x = asin((sin(25)/125)*240) = 54.235

we can solve for angle MBT since the sum of the angles in any triangle is 180 degrees:

180 - 25 - 54.235 = 100.77

as stated, angle MBG is supplemental to angle MBT:

angle MBG = 180 - 100.77 = 79.23

finally, angle GMB is based on the sum of the angles in a triangle equal to 180 degrees:

180 - 90 - 79.23 = 10.77

the angle the side of the hill makes with the horizontal is approximately 10.8 degrees