Question 213292
.13x+.04*30=.07(30+x)
.13x+1.2=2.1+.07x
.13x-.07x=2.1-1.2
.06x=.9
x=.9/.06
x=15 gallons of 13% acid is used.
Proof:
.13*15+.04*30=.07(30+15)
1.95+1.2=.07*45
3.15=3.15