Question 267345
.30x+.10(100-x)=.12*100
.30x+10-.10x=12
.20x=12-10
.20x=2
x=2/.2
x=10 gallons of 30% solution is used.
100-10=90 gallons 0f 10% is used.
Proof:
.30*10+.10*90=.12*100
3+9=12
12=12