Mr harper ,the candy store manager ,wants to mix butterscotch candies and cinnamon balls to make a d

题目

Mr harper ,the candy store manager ,wants to mix butterscotch candies and cinnamon balls to make a deluxe mix to sell for $3.00 a pound .butterscotch sells for $3.40 a pound ,while cinnamon balls sell for $2.90 a pound how many pounds of each should he use to make 20 pounds of the mix

答案

设butterscotch需x磅,则cinnamon balls需20-x磅
3.40x+2.90(20-x)=3.00*20
34x+29(20-x)=600
34x+580-29x=600
34x-29x=600-580
5x=20
x=4
20-4=16(pounds)