a+b=2
a+c=3
a+d=4
a+e=5
b+c=6
b+d=7
b+e=8
c+d=6
c+e=5
d+e=4
等式两边分别相加,得4（a+b+c+d+e）=50
a+b+c+d+e=12.5
a=12.5-(b+c)-(d+e)=12.5-6-4=2.5
b=12.5-(a+c)-(d+e)=12.5-3-4=5.5
c=12.5-(a+b)-(d+e)=12.5-2-4=6.5
d=12.5-(a+b)-(c+e)=12.5-2-5=5.5
e=12.5-(a+b)-(c+d)=12.5-2-6=4.5
答：这五个数为2.5,5.5,6.5,5.5,4.5