Question 964126
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S=amount of $7/lb coffee to add.
$13(70lbs)+$7(S)=$8(S+70lbs)
$910lbs+$7S=$8S+$560lbs Subtract $7s+$560lbs from each side.
$350lbs=$1SDivide by $1
350lbs=S She should add 350 lbs of the $7/lb coffee.
CHECK:
$13(70)+$7(350)=$8(420)
$910+$2450=$3360
$3360=$3360