簡單數學一題

let x be the number of $2 coin
so,3x is the no. of $1 coins.so,(x-5) is the no. of $5 coins
x(2)+3x(1)+(x-5)5=325
2x+3x+5x=325+25
10x=350
x=35
therefore.the number of $2 coins is 35

Let x be the number of $5 coins
The number of $2 coins is 5 more than the number of $5 coins
-> The number of $2 coins is x+5
The umber oh $1coins is three times that of $2coins
-> The number of $1 coins is 3(x+5)

The total value of Poon's coins is $325
-> 1*[ 3(x+5) ] + 2*(x+5) + 5*x = 325
3x + 15 + 2x + 10 + 5x = 325
10x + 25 = 325
10x = 300
x = 30

He has 30 $5 coins, 30+5 = 35 $2 coins and 3*35 = 105 $1 coins