Respuesta :

Its because the mathematical principle .

[tex]\\ \sf\bull\dashrightarrow 5+5=10[/tex]

  • Two 5s are added up to give 10.
  • So 5 is written alone

Note

  • (-)(-)=(+)
  • (+)(-)=(-)
  • (-)(+)=(-)
  • (+)(+)=(+)