Hi there, I believe the answer is 48 ft.
You can begin with drawing a right triangle. With the right triangle, the 80 ft ladder would be the side of the triangle that's leaning- the diagonal line or hypotenuse. Directly across from that, the leg, or the vertical line, would be considered the 64 ft building. The horizontal line is what you're looking for. This is looking like the Pythagorean theorem of a^2 + b^2 = c^2.
However, in this case, the "c" is the 80 because it is the hypotenuse and you can plug in the 64 as either a or b.
It should look something similar to this:
64^2 + b^2 = 80^2
You can work out the math from here by subtracting 64^2 from both sides and take that number to get the square root of b which should get you 48ft.
