2 17 - 9 = ( $) \begin{array} { l } ${$ \mathrm{ 想: } 9 + ($ ) = ( ) = ( ) }$ \end{array} 14 - 9 = ($ $) \begin{array} { l } ${$ \mathrm{ 想: } ($ ) + ( ) = ( ) } \\ {$ \quad \quad ($ ) - ( ) = ( ) }$ \end{array} 11 - 9 = ($ $) \begin{array} { l } ${$ \mathrm{ 想: } ($ ) + ( ) = ( ) } \\ {$ \quad \quad ($ ) - ( ) = ( ) }$ \end{array} 12 - 9 = ($ ) }$ \end{array} 18 - 9 = ($ ) } \\ {$ \quad \quad ($ ) + ( ) = ( ) }$ \end{array} 9 + 3 = ($ ) 12 - 9 = ( )
() + () = () () - () = () () + () = () () - () = () () + () = () () - () = ()

$17 - 9 = (8)$
想：$9 + (8) = (17)$，$17 - (9) = (8)$
$14 - 9 = (5)$
想：$(9) + (5) = (14)$，$(14) - (9) = (5)$
$11 - 9 = (2)$
想：$(2) + (9) = (11)$，$(11) - (9) = (2)$
$12 - 9 = (3)$
想：$10 - 9 = (1)$，$(1) + (2) = (3)$
$18 - 9 = (9)$
想：$10 - 9 = (1)$，$(1) + (8) = (9)$
$9 + 3 = (12)$
$12 - 9 = (3)$
$(9)+(3)=(12)$
$(12)-(9)=(3)$
$(7)+(5)=(12)$
$(12)-(5)=(7)$（答案不唯一，以第一组为例）
$(6)+(6)=(12)$
$(12)-(6)=(6)$（答案不唯一，以第一组为例）
$(7)+(5)=(12)$
$(12)-(5)=(7)$（答案不唯一，以第一组为例）