Solve: 
1)  How many pounds of coffee worth $3.30 a pound should be mixed with 70 pounds of coffee worth $2.30 a pound do produce a mixture worth $2.60 a pound?

2)  A gas station owner has 40 gallons of gasoline worth $1.30 per gallon and some worth $2.30 per gallon. How many gallons of the $2.30 brand must the owner mix in to produce gasoline that costs $1.80 per gallon? 
3)  A 10 kg nut mixture that is 50% peanuts is combined with 10 kg of an 70% peanut mixture. What percent of the new mixture is peanuts?

4)  How many pounds of coffee worth $2.50 a pound should be mixed with 80 pounds of coffee worth $1.70 a pound do produce a mixture worth $1.86 a pound? 
5)  A certain liquid is 96% water. Some of the water evaporates, leaving a liquid that is 95% water. How much of the water evaporated?

6)  A 2 kg nut mixture that is 50% peanuts is combined with 38 kg of an 70% peanut mixture. What percent of the new mixture is peanuts? 