Question 1154236
[ number of items bought ] = [ total amount spent ] / [ price / item ]
number of items Sue could buy =
{{{ 14 / (( d + k*m )/ m ) }}}
{{{ ( 14m ) / ( d + k*m ) }}}
{{{ 14 / (( d/m + k )) }}} answer
----------------------------------
check:
suppose 
{{{ m = 9 }}}
{{{ d = 18 }}}
{{{ k = 5 }}}
{{{ m = 9 }}} items for $18 is $2 / item
If the price is raised to {{{ 2 + k = 7 }}} / item
With $14 she can buy:
{{{ 14 / 7 = 2 }}} items
--------------------------
Use the formula:
{{{ 14 / ( d/m + k ) }}} 
{{{ 14 / ( 18/9 + 5 ) }}}
{{{ 14 / 7 = 2 }}} items
Get a 2nd opinion if needed