Question

tìm x, biết :

[ (6x - 39 ) : 7 ] . 4 = 12

( x : 3 - 4 ). 5 = 15

x - [ 42 + ( -28 ) ] = -8

 

Answer 1

[ ( 6x - 39 ) : 7 ] . 4 = 12

=> ( 6x - 39 ) : 7 = 12 : 4

=> ( 6x - 39 ) : 7 = 3

=> 6x - 39 = 3.7

=> 6x - 39 = 21

=> 6x = 21+39

=> 6x = 60

=> x = 10.

( x : 3 - 4 ) . 5 = 15

=> x : 3 - 4 = 15 : 5

=> x : 3 - 4 = 3

=> x : 3 = 7

=> x = 7.3

=> x = 21

x - [ 42 + (-28) ] = -8

=> x - 14 = -8

=> x = -8 + 14

=> x = 6.

Answer 2

[ (6x - 39): 7] . 4=12

(6x-39) : 7=12:4

(6x -39) :7=3

(6x-39) =3 . 7

6x-39 =21

6x =21 +39

6x=20

x=10

Answer 3

(x :3 -4) .5 =15

(x : 3 -4) =15:5

x:3-4 =3

x : 3=3+4

x:3 =7

x=7 . 3

x=21

Answer 4

x - [42 -28 ] =-8

x- 14=88

x=-8+14=22