39 + (31 - x) = 70
31 - x = 70 - 39
31 - x = 31
x = 31 - 31
x = 0
39 + ( 31 - x ) = 70
31 - x = 70 - 39
31 - x = 31
x = 31 - 31
x = 0 .
39+(31-x)=70
(31-x)=70-39
(31-x)=31
x=31-31
x=0
Vậy x=0
39+(31-x)=70
x = 70 - 39
x = 31
x = 31 - 31
x = 0
31 - x = 70 - 39
31 - x = 31
X = 31 - 31
X = 0
39 + ( 31 - x ) = 70
31 - x = 70 - 39
31 - x = 31
x = 31 - 31
x = 0
chúc bn hc tốt ^^