Question 1093406
The expression "must be used to make" is misleading. 
I assume that the company started with pure 100% juice. 
Wouldn't it be easier and cheaper just to dilute some 100% juice to make the 60% juice drink instead of spending time and money to further dilute already prepared drinks. Basically, a poorly conceived and written problem.
.45x+.70y=.60*140
.45x+.70y=84
x+y=140