75883-(31206+x)=999
(31206+x)=75883-999
31206+x=74884
x=74884-31206
x=43678
ta có 75883 - ( 31206 + x) = 999 => 75883 - 31206 - x = 999 => 44677 - x = 999 => x = 44677 - 999 => x= 43678
vậy x= 43678
75883-(31206+x)=999
(31206+x)=75883-999
(31206+x)=74884
x=74884-31206
x=43678
<=> 31206+x=75883-999=74884
<=> x=74884-31206=43678