Q:
sean wants to make a mixture that is 50% lemon juice and 50% lime juice.
how much 100% lemon juice should he add to a juice mixture that is 30% lemon juice and 70% lime juice to make 7 gal of the 50% lemon/50% lime juice mixture?
note:
i'm struggling with this problem as i don't know how to go about solving it. could someone me and explain what to do?

Item 1 which question could the expression 1000n answer? let n = the number of gallons of gas used. how many miles per gallon did the car get driving 1000 miles? let n = the number of grams of food needed for each dog. how many grams of food are needed to feed 1000 dogs? let n = the number of people at the show. how many empty seats were there at the show if there are 1000 seats at the theater? let n = the number of seats at the theater. how many empty seats will there by if 1000 people come to the show?