6 lbs of potatoes cost $12.90. How much would 3.4 lbs cost?

6lbs = 3.4 lbs

$12.90 x

6lbs x=($12.90 )(3.4 lbs)

6lbs x=43.86$lbs

6lbs x/6lbs=43.86$lbs/6lbs

x=$7.31