x+y+z=55 y+z+w=58 x+y+w=62 x+z+w=65
问题描述：
x+y+z=55 y+z+w=58 x+y+w=62 x+z+w=65
答
x+y+z=55 ①
y+z+w=58 ②
x+y+w=62 ③
x+z+w=65 ④
①+②+③+④得3（x+y+z+w）=240
于是x+y+z+w=80 ⑤
⑤-①得 w=25
⑤-②得 x=22
⑤-③得 z=18
⑤-④得 y=15