Question 442717
The way to think of it is: If a patio loses 3 inches of height 
for every 15 feet of its length, what is its slope?
Slope is defined as:
(change in y) / (change in x)
These changes have to be in the same units, so 
{{{15}}} feet * {{{12}}} inches/foot = {{{180}}} inches
change in y = {{{3}}} inches
change in x = {{{180}}} inches
(change in y) / (change in x) = {{{3/180}}}
{{{ 3/180 = 1/60 }}}
The slope is 1/60