Theorem 3p6e9

Description: 3 + 6 = 9. (Contributed by SN, 24-Aug-2026)

	Ref	Expression
Assertion	3p6e9	$$⊢3+6=9$$

Proof

Step	Hyp	Ref	Expression
1		3cn	$$⊢3\in ℂ$$
2	1 1 1	addassi	$$⊢3+3+3=3+3+3$$
3		3p3e6	$$⊢3+3=6$$
4	3	oveq1i	$$⊢3+3+3=6+3$$
5		6p3e9	$$⊢6+3=9$$
6	4 5	eqtri	$$⊢3+3+3=9$$
7	3	oveq2i	$$⊢3+3+3=3+6$$
8	2 6 7	3eqtr3ri	$$⊢3+6=9$$