Question 388392
Let A be the number of $11.50 disks, B the number of $7.50 disks,
1.{{{A+B=12}}}
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{{{1150A+750B=11000}}}
2.{{{23A+15B=220}}}
Multiply eq. 1 by (-15) and add to eq. 2,
{{{-15A-15B+23A+15B=-180+220}}}
{{{8A=40}}}
{{{highlight(A=5)}}}
Then from eq. 1,
{{{5+B=12}}}
{{{highlight(B=7)}}}
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