( )
438=51 1650=66 809=89
6840=28 2430=54 764=72
=(个)
12 - 5 =
19 - 7 =
41 - 8 =
17 + 8 =
34 + 6 =
41 + 30=
25 - 9 =
31 - 5 =
15
10
7
( )?