I am working through Karen Smith's An Invitation to Algebraic Geometry, and I am confused with the following problem from the text.
Let $R$ be a $\mathbb{C}$-algebra, and let $I$ be an ideal of $R$. Prove that the natural surjection $R\rightarrow R/I$ is a $\mathbb{C}$-algebra map.
The reason this question confuses me is that she defines a $\mathbb{C}$-algebra to be a ring $R$ that contains $\mathbb{C}$ as a subring. Furthermore, a $\mathbb{C}$-algebra map is not defined, but a $\mathbb{C}$-algebra homomorphism is defined, so I am assuming the two are the same. She defines a $\mathbb{C}$-algebra homomorphism as follows:
If $R$ and $S$ are $\mathbb{C}$-algebras, then a map $$R\xrightarrow\phi S$$ is said to be a $\mathbb{C}$-algebra homomorphism if it is a ring map (homomorphism) and if it is linear over $\mathbb{C}$, that is, $\phi(\lambda r)=\lambda\phi(r)$ for all $\lambda\in\mathbb{C}$ and $r\in R$.
The reason this is confusing me is that if $I$ is an ideal such that $R/I$ is not a $\mathbb{C}$-algebra, then we can't have a $\mathbb{C}$-algebra map as defined. Thus, should I be making the assumption that $R/I$ is a $\mathbb{C}$ algebra or is one of the definitions incorrect. I am just stuck on trying to even parse where to start on the problem as it seems to me that it might not be true with the given definitions as clearly if we take $I=R$, then $R/R$ is clearly not a $\mathbb{C}$-algebra as defined.