Question 1103081
If it is from upper left to lower left (left both times),
and it is a rectangular painting and it is not hanging crooked,
The line from upper left to lower left is vertical,
and the slope of a vertical line is undefined.
The slope is the vertical increase divided by
the horizontal displacement to the right,
which in that case is zero, and division by zero is not defined.
 
Now, for a properly hung rectangular painting with those dimensions,
from upper left to lower right,
you would gain {{{-7}}} meters in height,
as you moved {{{4}}} meters to the right,
for a slope of {{{-7/4=-1.75}}} .