Theorem addassnni

Description: Associative law for addition. (Contributed by metakunt, 25-Apr-2024)

	Ref	Expression
Hypotheses	addassnni.1	$$⊢A\in \mathbb{N}$$
	addassnni.2	$$⊢B\in \mathbb{N}$$
	addassnni.3	$$⊢C\in \mathbb{N}$$
Assertion	addassnni	$$⊢A+B+C=A+B+C$$

Proof

Step	Hyp	Ref	Expression
1		addassnni.1	$$⊢A\in \mathbb{N}$$
2		addassnni.2	$$⊢B\in \mathbb{N}$$
3		addassnni.3	$$⊢C\in \mathbb{N}$$
4	1	nncni	$$⊢A\in ℂ$$
5	2	nncni	$$⊢B\in ℂ$$
6	3	nncni	$$⊢C\in ℂ$$
7	4 5 6	addassi	$$⊢A+B+C=A+B+C$$