Question 972933
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R=pounds of raisins; B=pounds of bran=12lbs; M=pounds of mix=R+B=R+12lbs
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$4.50/lb(R)+$2.80/lb(B)=$3.14/lb(M) Substitute for M.
$4.50/lb(R)+$2.80/lb(12lb)=$3.14/lb(R+12lb)
$4.50/lb(R)+$33.60=$3.14/lb(R)+$37.68 Subtract ($3.14/lb(R)+$33.60) from each side.
$1.36/lb(R)=$4.08/lb Divide each side by $1.36/lb.
R=3lb ANSWER You Should add 3 lbs of raisins to 12 lbs of bran flakes.
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CHECK:
$4.50/lb(R)+$2.80/lb(B)=$3.14/lb(R+B)
$4.50/lb(3lbs)+$2.80/lb(12lbs)=$3.14/lb(15lbs)
$13.50+$33.60=$47.10
$47.10=$47.10