设5个数为x1,x2,x3,x4,x5
(x1+x2+x3+x4+x5)/5=102
x1+x2+x3+x4+x5=510.(1)
x1+x2+x3=70*3=210.(2)
x3+x4+x5=130*3=390.(3)
(2)式+(3)式-(1)式得x3=210+390-510=90
设5个数为x1,x2,x3,x4,x5
(x1+x2+x3+x4+x5)/5=102
x1+x2+x3+x4+x5=510.(1)
x1+x2+x3=70*3=210.(2)
x3+x4+x5=130*3=390.(3)
(2)式+(3)式-(1)式得x3=210+390-510=90