Question 1158384
want 6  oz 0.08 fuel=0.48 fuel-oz
have x os .04 fuel=.04x fuel-oz
and 6-x oz .20 fuel=1.20-.20x fuel-oz

so .04x+1.20-.20x=0.48
-.16x=-.72
x=4.5 oz of 4% 
6-x=1.5 oz of 20% 

4.5 ounces of 4% ANSWER