[tex]\dfrac{8}{10}-(\dfrac{9}{10}-x)=\dfrac{4}{10}[/tex]
[tex]\dfrac{8}{10}-\dfrac{9}{10}+x=\dfrac{2}{5}[/tex]
[tex]\dfrac{8-9}{10}+x=\dfrac{2}{5}[/tex]
[tex]\dfrac{-1}{10}+x=\dfrac{2}{5}[/tex]
[tex]x=\dfrac{2}{5}+\dfrac{1}{10}[/tex]
[tex]x=\dfrac{4+1}{10}[/tex]
[tex]x=\dfrac{5}{10}[/tex]
=simplifici cu 5=
[tex]x=\dfrac{1}{2}[/tex]
[tex](x=1:2=0,5)[/tex]