MATHS 英文題方程式

(a)

Let Peter has $P, where $P is $y more than $x. That is P = x + y. (Please double check if you have missed out y when typing the question.)

Total amount of money that John and Peter have = $x + $P = $x + ($x + $y) = 2* $x + $y

David has $2 more than the total amount of money that John and Peter have. So David has $2 + 2* $x + $y

They totally have ($2 + 2* $x + $y) + 2* $x + $y = $100
This means that $2 + 4* $x + 2* $y = $100
4* $x + 2* $y = $98
2* $x + $y = $49 (equation 1)

After you find out what is $y from the exercise book, you should be able to find out what is $x and thus the amount of money that John and Peter has.

To recap,
John has $x, Peter has $x + $y.

As for David, he has $2 + 2* $x + $y. From equation 1 above, 2* $x + $y = $49. So David has $2 + $49 = $51.



(b)

18 * $5 + 3 * $2 = $96
16 * $5 + 8 * $2 = $96
14 * $5 + 13 * $2 = $96
12 * $5 + 18 * $2 = $96

So the boy has 4 ways (listed above) to pays the exact price for the gift.