第三天还有蟠桃:
(1+1)÷(1-1/2)
=2÷1/2
=4(个)
第二天还有蟠桃:
(4+2)÷(1-1/3)
=6÷2/3
=9(个)
原共有蟠桃:
(9+3)÷(1-1/4)
=12÷3/4
=16(个)