Aman standing near a building notices trhat the angle of elevation to the top of the buiilding is 64. he then walks 240 feet farther away from the building and finds the angle of elevation to the top to be 43. how tall is the building

See the picture attached to better understand the problem
 we know that
in the right triangle ABC
tan 64°=AB/AC------> AB=AC*tan 64°-----> AB=x*tan 64°---> equation 1

in the right triangle ABD
tan 43°=AB/DA----> AB=DA*tan 43°---> AB=(240+x)*tan 43°---> equation 2

equate equation 1 and equation 2
x*tan 64°-=(240+x)*tan 43°---->x*tan 64=240*tan 43+x*tan 43
x*[tan 64-tan 43]=240*tan 43-----> x=240*tan 43/[tan 64-tan 43]
x=200.22 ft

AB=x*tan 64----> AB=200.22*tan 64-----> AB=410.51 ft

the answer is
410.51 ft

Do the inverse operation