[tex]5,5x=4[/tex]
[tex]x=4:5,5[/tex]
[tex]x=4:\frac{11}{2}[/tex]
[tex]x=4*\frac{2}{11}[/tex]
[tex]x=\frac{8}{11}[/tex]

[tex]\boxed{Otvet:x=\frac{8}{11}}[/tex]

Пошаговое решение:

[tex]\displaystyle \frac{55}{10}*x=\frac{40}{10}\\\\ x=\frac{40}{10}:\frac{55}{10}\\\\x= \frac{40*10}{10*55}\\\\x=\frac{400}{550}\\\\ x=\frac{8}{11}[/tex]