设小红体重x,小明y,小丽z
x+y=16...(1)
x+z=21.5...(2)
y+z=22.5...(3)
(1)+(2)+(3)
2(x+y+z)=16+22.5+22.5
2(x+y+z)=61
x+y+z=61/2
x+y+z=30.5...(4)
(4)-(1) 小丽体重z=30.5-16=14.5
(4)-(2) 小明体重y=30.5-21.5=9
(4)-(3) 小红体重x=30.5-22.5=8
设小红体重x,小明y,小丽z
x+y=16...(1)
x+z=21.5...(2)
y+z=22.5...(3)
(1)+(2)+(3)
2(x+y+z)=16+22.5+22.5
2(x+y+z)=61
x+y+z=61/2
x+y+z=30.5...(4)
(4)-(1) 小丽体重z=30.5-16=14.5
(4)-(2) 小明体重y=30.5-21.5=9
(4)-(3) 小红体重x=30.5-22.5=8