標題:

please show me step by step solving this question?

發問:

donna buys $2 stamps and $5 stamps. If she spend $54 altogether and get 15 stamps. how many $2 stamps she buy? the age of a father and son now add up to 40. In six years, the difference in their ages will be 24 years. what are their ages now?

• f.4 maths trigonometry
• 會考Maths grade~~~~2007
• 依家既彩雲國物語第二季又做到第幾集

• f.4 maths trigonometry
• 會考Maths grade~~~~2007
• 依家既彩雲國物語第二季又做到第幾集

 

此文章來自奇摩知識+如有不便請留言告知

最佳解答:

donna buys $2 stamps and $5 stamps. If she spend $54 altogether and get 15 stamps. how many $2 stamps she buy? ANS: Let x and y be the no. of $2 and $5 stamps Donna bought respectively. x+y=15..............(1) 2x+5y=54...........(2) (1)X5:5x+5y=75......(3) (3)-(2):3x=21 x=7 the age of a father and son now add up to 40. In six years, the difference in their ages will be 24 years. what are their ages now? ANS: Let x and y be the ages of the father and son respectively. x+y=40......(1) (x+6)-(y+6)=24 x-y=24..........(2) (1)+(2):2x=64 x=32 Sub. x=32 into(1), y=8

其他解答:

1. Let y be the number of $2 stamps she buy. 2y+5(15-y)=54 2y+75-5y=54 -3y=54-75 -3y=-21 y=7 She buys 7 $2 stamps. 2.Let y be the age of the father. y+(y-24)=40+6 y+y-24=40+6 2y=46+24 2y=70 y=35 The age of the father is 35 and the age of the son 40-35=5 now.