5x+7y=231,7x+5y+18=231
两式相加
12x+12y+18=462
12x+12y=444
x+y=37
y=37-x
7x+5(37-x)+18=231
7x-5x+185+18=231
2x=231-203
x=28
x=14
y=37-14=23