Question 1035257
Hi there,
Consider labeling the painting
on the wall ABCD
AB being the top
CD being the bottom
Its corresponding part on
the floor will be labeled
CDEF.
CD being the bottom of
the wall part, but the top 
of the floor part.
EF being the bottom of
the floor part.
First we calculate CF which is 
the floor diagonal.
CE^2 + EF^2 = CF^2
10^2 + 12^2 = CF^2
CF^2 = 244
CF = √244
CF = 15.62 feet.
Now, we use the triangle
ACF to calculate the distance
from the top left corner to the 
bottom right
AC^2 + CF^2 = AF^2
10^2 + 15.62^2 = AF^2
AF = √343.9844
AF = 18.55 feet (2 decimal places)
Hope this helps :-)