$\mathbb Z$ (Our usual notation for the integers) with a little subscript at the bottom.
This is the question being asked:
what are the subgroups of order $4$ of $\mathbb Z_2 \times\mathbb Z_4$ ($\mathbb Z_2$ cross $\mathbb Z_4$)
Give them as sets and identity the group of order 4 that each of the subgroup is isomorphic to
I was thinking that it meant the set of integers modulo $4$ and modulo $2$, but I'm not too sure
Give them as sets and identity the group of order $4$ that each of the subgroup is isomorphic to
What is the definition of "order". I couldn't really find that anywhere either.