A mixture of coffee worth $1.20 a pound and of coffee worth $1.80 a pound is valued at $18.00. If the price per pound of each grade is increased $.30, the new value of the mixture would be $21.30. Find the number of pounds of coffee for each grade.

Guys, this problem is from an algebra text, so no multiple choice answers...but I've seen something like it before on GMATprep. Can't seem to wrap my head around this one...thanks for your help.

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