Let 'x' be the amount of pepper mints ($1.20 per pound)
'y' be the amount of chocolates ($2.40 per pound)
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-The whole mixture amounts to 40 lbs.
x + y = 40 ----------equation 1
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-The mix is $1.65 per pound
1.2x + 2.4y = 40(1.65)
1.2x + 2.4y = 66 ----equation 2
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From equation 1
x + y = 40
x = 40 - y ----equation 3
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Substitute equation 3 to equation 2
1.2x + 2.4y = 66
1.2(40-y) + 2.4y = 66
48 - 1.2y + 2.4y = 66
-1.2y + 2.4y = 66 - 48
1.2y = 18
y = 15 lbs
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Substitute y=15 to equation 3
x = 40 - y
x = 40 - 15
x = 25 lbs
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Therefore 15 lbs of chocolates and 25 lbs of pepper mints will be used.