Theorem 1p6e7

Description: 1 + 6 = 7. (Contributed by SN, 24-Aug-2026)

	Ref	Expression
Assertion	1p6e7	$$⊢1+6=7$$

Proof

Step	Hyp	Ref	Expression
1		df-6	$$⊢6=5+1$$
2	1	oveq2i	$$⊢1+6=1+5+1$$
3		ax-1cn	$$⊢1\in ℂ$$
4		5cn	$$⊢5\in ℂ$$
5	3 4 3	addassi	$$⊢1+5+1=1+5+1$$
6		1p5e6	$$⊢1+5=6$$
7	6	oveq1i	$$⊢1+5+1=6+1$$
8		6p1e7	$$⊢6+1=7$$
9	7 8	eqtri	$$⊢1+5+1=7$$
10	2 5 9	3eqtr2i	$$⊢1+6=7$$