Es seien ${\displaystyle {}a,b,c}$ natürliche Zahlen mit ${\displaystyle {}a,b\geq c}$. Zeige

${\displaystyle {}(a-c)+b=a+(b-c)\,.}$

Gilt

${\displaystyle {}(8-5)+3=8+(3-5)\,}$

${\displaystyle {}\mathbb {N} }$