X = 30−19X = 19

7 : - DE THI HK
Toán DE THI HK
7

: x =

30−19

x =

19

:

−87

(0,25đ)

x =

57

:

30−19

x =

19

.

−78

x =

57

.

19−30

x =

63−8

(0,25đ)

x =

133−150

(0,25đ)