SOLUTION: how many quarts of pure anitfreeze must be added to 2 quarts of a 10% antifreeze solution to obtain a 30% antifreeze solution?

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Question 263101: how many quarts of pure anitfreeze must be added to 2 quarts of a 10% antifreeze solution to obtain a 30% antifreeze solution?
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
2*.10+x=(2+x)*.3
2*.10+x=2*.3+x*.3
.2+x=.6+.3x
.7x=.4
x=4/7quart or 0.571429 quart
check
2*.1+4/7=2 4/7*.3
2/10+4/7=18/7*3/10
14/70+40/70=3*18/70
54/70=54/70
ok
use fraction instead of decimals
2/10+x=3(2+x)/10
2/10+10x/10=6+3x/10
2+10x=6+3x
7x=4
x=4/7