Question 1072873
<pre>
Let x = the number of refrigerators
Let y = the number of upright pianos

{{{300x+525y}}}{{{""<=""}}}{{{6800}}}

We graph the boundary line:

{{{300x+525y}}}{{{""=""}}}{{{6800}}}

Divide through by 25 to simplify:

{{{12x+21y}}}{{{""=""}}}{{{272}}}

The intercepts are {{{(matrix(1,3,0,",",12&20/21))}}} and {{{(matrix(1,3,22&2/3,",",0))}}}

We draw the boundary line, and shade below it because the
origin used as a test point:

{{{300(0)+525(0)}}}{{{""<=""}}}{{{6800}}}
{{{0}}}{{{""<=""}}}{{{6800}}} 

gives a true inequality

{{{drawing(450,72000/269,-1.9,25,-1,15,30,
line(-17,22+2/3,32,-5-1/3),
graph(450,72000/269,-1.9,25,-1,15,30,y<(272-12x)/21-.2),
graph(450,72000/269,-1.9,25,-1,15,30)
)}}}

Will 10 refrigerators and 9 pianos overload the truck?

The points inside or on the boundary of the shaded region
represent the loads the truck can carry.  The x-coodinate
is the number of refrigerators, and the y-coordinate is
the number of pianos.

We plot the point (10,9) and see if it is in the shaded region:

{{{drawing(450,72000/269,-1.9,25,-1,15,30,
line(-17,22+2/3,32,-5-1/3), circle(10,9,.2),
 circle(10,9,.175), circle(10,9,.15), circle(10,9,.1),
 circle(10,9,.05), circle(10,9,.02), circle(10,9,.08),
 locate(10,9,"(10,9)"),
graph(450,72000/269,-1.9,25,-1,15,30,y<(272-12x)/21-.2),
graph(450,72000/269,-1.9,25,-1,15,30)
)}}}

The point (10,9) is outside the shaded region, so yes,
10 refrigerators and 9 pianos will overload the truck.

Edwin</pre>