I have beans that sell for $9 per pound and $12 per pound, they need to be mixed to create 100lbs of mixture that will sell for $11.25 per pound . How much of each type of bean should be used in the mixture?

Question

X=#lbs beans that sell for $9.00/lb.
Y=#lbs beans that see for $12.00/lb.
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X+Y=100 eqn 1 equates to total lbs.
9X + 12Y = 100*11.25=1125 eqn 2 is cost.
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Two equations. Two unknowns. Solve simultaneously.

Post your work if you get stuck.