Question 1038869
I notice 2 things about problem:
(1)
All data is in terms of yds, so there is no need to 
convert to ft
(2)
They don't tell you what size tiles to use, so there
is no way to determine the number of tiles.
All you can do is show the AREA of the tiled surface
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Let {{{ A[y] }}} = the area of the backyard
Let {{{ A[p] }}} = the area of the pool
{{{ A[y] - A[p] }}} = the tiled area
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{{{ A[y] = 15*17 }}}
{{{ A[y] = 255 }}} yd2
and
{{{ A[p] = 7*7 }}}
{{{ A[p] = 49 }}} yd2
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{{{ A[y] - A[p] = 255 - 49 }}}
{{{ A[y] - A[p] = 206 }}} yd2
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The area of the tiles needed is 206 square yds