carl has $9 more than david does.hilbert has 1/3 of the amout of carl.if they have a total amout of $61,how much does each of them have?

　　Carl 的钱比David多9 美元，Hilbert的钱是Carl的1/3，如果他们三人一共有61美元，他们三人各有多少美元？
设Carl 有x美元
　∴David有(x-9)美元
　　Hilbert有(x/3)美元
　∴x+(x-9)+(x/3)=61
　　7x=210
　　x=30
　∴x-9=30-9=21
　　x/3=30÷3=10
答：Carl 有30美元，David有21美元，Hilbert有10美元

Let $x be the amount of Carl has,$(x-9) be the amount of David has and $(x/3) be the amount of Hibert.
x+(x-9)+(x/3)=61
7x-27=183
7x=210
x=30
Carl has $30,David has $21 and Hibert has $10