【How-to】How many elements does s3 have

Thus there are 10 subgroups of D8: the trivial subgroup, the six cyclic subgroups {e, s, s2,s3},{e, s2},{e, rx},{e, ry},{e, rx+y}, and {e, rx−y}, the two subgroups {e, s2,rx,ry} and {e, s2,rx+y,rx−y}, and D8. (4b) Show that D8 is not isomorphic to Q8.