Question 1062362
small=x
medium=y
large=z

x+y+z=21
9x+10y+13z=220
y=z+1
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x+y+z=21
9x+10y+13z=220
y-z=1
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first times -9 and add it to second

9x+10y+13z=220
-9x-9y-9z=-189
y-z=1

y+4z=31
y-z=1
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multiply the third one by -1 and add to second
y+4z=31
-y+z=-1
5z=30
z=6
y=z+1
y=7
x+y+z=21, x=8
{8,7,6}
8*$9=$72
7*$10=$70
6*$13=$78
Total=21 and $220