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Groups and FieldsEasyHomomorphisms and Isomorphisms

Homomorphisms and Isomorphisms · Easy problem

A homomorphism φ:Z10→Z10\varphi: \mathbb Z_{10} \to \mathbb Z_{10} satisfies φ(1)=7\varphi(1) = 7. What is φ(23)\varphi(23) (as an element of {0,1,…,9}\{0,1,\dots,9\})?