SOLUTION: How many gallons of a 30% acid solution must be mixed with 50 gallons of a 70% acid solution to make a 55% solution?

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Question 335325: How many gallons of a 30% acid solution must be mixed with 50 gallons of a 70% acid solution to make a 55% solution?
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
.30x+.70*50=.55(50+x)
.30x+35=27.5+.55x
.30x-55x=27.5-35
-.25x=-7.5
x=-7.5/-.25
x=30 gallons of 30% solution.
Proof:
.30*30+.70*50=.55(50+30)
9+35=.55*80
44=44