987654321
98765432
(a)2
98765432÷249382716
49382716195
(b)(a)2
49382716÷2=24691358
246913587
(c)(b)2
24691358÷212345679
123456798
(d)(c)5
12345679×5=61728395
61728395缺4
(e)(d)(b)
61728395+24691358=86417953
86417953缺2
(f)9(a)(e)
19888888888
(a)59444444444
(b)79222222222
(C)89111111111
(d)49555555555
(e)29777777777
n9(9-n)