Tìm các giá trị thích hợp của chữ số $a$ sao cho: $- \overline {a99}  >  - 649 >  - \overline {6a0}$

$- 5 <  - 2$

$0 < 4$                            

$0 >  - 1$                          

$- 5 <  - 6$

$20$                         

$- 17$                            

$- 18$                          

$- 20$

$- 7; - 6; - 4;0;3;14$   

$- 4; - 6; - 7;0;3;14$

$14;3;0; - 4; - 6; - 7$   

$- 6; - 7; - 4;0;3;14$

$A = \left\{ { - 8; - 7; - 6; - 5; - 4; - 3; - 2; - 1} \right\}$                        

$A = \left\{ { - 9; - 8; - 7; - 6; - 5; - 4; - 3; - 2; - 1} \right\}$

$A = \left\{ { - 9; - 8; - 7; - 6; - 5; - 4; - 3; - 2; - 1;0} \right\}$               

$A = \left\{ { - 8; - 7; - 6; - 5; - 4; - 3; - 2; - 1;0} \right\}$

$- 12$    

$- 11$            

$- 10$            

$12$