Answer:
The third wine costs $5.70 per litre
Step-by-step explanation:
so we've got 2 parts $4.50 wine, 3 parts $5 wine and 4 parts x wine. The result is $5.20 per part.
2l*$4.50/l + 3l*$5/l + 4l*x = (2l+3l+4l)*$5.20/l
$9 + $15 + 4l*x = $46.80
4l*x = $22.80
x = $5.70/l
