For his birthday party jacob mixed together 8 gal. of brand a fruit punch and 2 gal. of brand b. brand a contains 60% fruit juice an brand b contains 10% fruit juice. what percent of the mixture is fruit juice?

The answer is 5 gallons
Its very simple. 
Turn 60% and 10% into decimals ( .60 and .10)
Multiply 8 gallons ( brand A ) by .60 and you get 4.8 gallons
Multiply 2 gallons ( brand B ) by .10 and you get .2 gallons
Add them up and you get 5 gallons.