Question 71527
Let x=number of pounds of $4.20 tea

Cost of $4.20 tea ($4.20x) plus cost of $2.25 tea ($2.25*12) must equal cost of final mixture (x+12)($3.40).  So our equation to solve is:

$4.20x+$2.25*12=$3.40(x+12)  get rid of parens and simplify

$4.20x+$27.00=$3.40x+$40.80  subtract $27.00 and also $3.40x from both sides

$4.20x+$27.00-$27.00-$3.40x=$3.40x-$3.40x+$40.80-$27.00  collect like terms

$.8x=$13.80  divide both sides by $.8

x=17.25 lb-------------------number of lbs of $4.20 tea

CK
$4.20(17.25)+$2.25(12)=$3.40(29.25)
$72.45+$27=$99.45
$99.45=$99.45

Hope this helps----ptaylor