Question 224869
.10x+.02(40-x)=.08*40
.10x+.8-.02x=3.2
.10-.02x=3.2-.8
.08x=2.4 
x=2.4/.08
x=30 gal. of 10% mix is used.
40-30=10 gal. of 2% mix is used.
Proof:
.10*30+.02*10=3.2
3+.2=3.2
3.2=3.2