The answer is x-4=9 because it is 4 LESS than a number that equals 9. x would equal 9+4 which is 13.
Distance from the building where the fireman is standing = 25 m due yo the west pointed angle of elevation of the ladder = 51 degrees You then aquire the length of the ladder equals...
x ThenCos 51 degree = 25/x0.6293
= 25/xx = 25/0.6293 = 39.72 meters≈40 meters from the above deduction, so the correct answer is D, because it is the closest, and that it is correct.