Question

Tìm x biết:

31-(21+x)=13-(-17+11)

Answer 1

31-(21+x)=13-(-17+11)

31-(21+x)=13-(-6)

31-(21+x)=13+6

31-(21+x)=19

21+x=31-19

21+x=12

x=12-21

x=-9

Answer 2

Ta có: \(31-\left(21+x\right)=13--6=13+6=19\)

\(\Rightarrow21+x=31-19=12\)

\(\Rightarrow x=-9\)

Vậy: \(x=-9\)

Answer 3

\(31-\left(21+x\right)=13-\left(-17+11\right)\)

\(31-12-x=13+17-11\)

\(19-x=19\)

\(x=0\)