因为：xy=(x-10)(y+1)→xy=xy+x-10y-10 ①
xy=(x-15)(y+3) →xy=+3x-15y-45 ②
由①、②得：x=10y+10 ③
x=5y+15 ④
将③‐­ ④得：10y+10 =5y+15 →y=1
将 y=1代入③得：x=20