Question 600276
Let {{{ x }}} = the maximum 
number of 4 pound bags
of apples the cafeteria can buy.
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{{{ y }}} is the maximum
number of 7 pound bags of
apples the cafeteria can buy
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{{{ 4x + 7y <= 28 }}}
{{{ 7y <= -4x + 28 }}}
{{{ y <= -(4/7)*x + 4 }}}
Here's the graph. All the possible solutions
lie on the line and under the line 
and bounded by the
x and y axes
{{{ graph( 400, 400, -2, 10, -2, 10, -(4/7)*x + 4 ) }}}