      !"#$%  !"#$%& '()(*+ ,-. /  0)(.$1 !234&.*+56 (- 7  8(2/  0)(9:;$<=.$1 ->2.$1 7 ?<@ =A56 (-)( (;(B;C(B; <@"D(B;"-E & '()&*%  '+,-.% &/0F G ;1A HA/ *(-F (E     − + 5E   I  J −  E  E     C +  3E 2KI  J− LE K K 2KI 2KI       − + −  ÷  ÷     ME       F F K  K K  K     − − + − +  ÷  ÷     N E    I     − +  ÷    E   −  ÷   2 2 3 1: 3 4  ;E    KI     − −  ÷    OE   K K K I K I  BEPC2JEI2QCR2I2ESFP2KI2KC2KEI2KS &/0F G ;1A HA/ F (E R  IJ F  2 K K     − +  ÷  ÷     5E     IR I J  J  − E  K  T 2K     + − + + &/0F/ F 12  R T   K  K + + +  32 K K  J     + − − &/0F UBV25;WF(2     =+ − x 52    F   K x+ = 2    F2J F 2   x= 32    x − = N &/04F(EUB (;*+V"D&5;WF   x y = "DVQ&XJ 5EUB (;*+V"D&5;WVFX&FCKE"DVY&X &/05FUB5(*+V2&2Z5;W?6F 2    K x y y z = = "DVQ&YZX  &*-'6"7% &/08FSố học sinh của bốn khối 6 , 7, 8, 9 tỉ lệ với các số 9 , 8 , 7 ,6 . Biết rằng số h[*; khối 9 ít hơn số hs khối 7 là 70 h[*; . 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Biết rằng số h[*; khối 9 ít hơn số hs khối 7 là 70 h[*; . Tính số h[*;. '()(*+ ,-. /  0)(.$1 !234&.*+56 (- 7  8(2/  0)(9:;$<=.$1 ->2.$1 7 ?<@ =A56 (-)( (;(B;C(B; <@"D(B;"-E &. 1*+a$1O)(&9+;";VI "Fde 37 0 4 3 2 1 4 3 2 1 B A b a ? 110 0 C D B A n m   524&5;f-3;g& L^VI 2/ ; ?7 )(&O ;VXKNVXI &/0%