isabelle/valid/mathd_algebra_224.thy (11 lines of code) (raw):
(*
Authors: Wenda Li
*)
theory mathd_algebra_224
imports Complex_Main "HOL-Computational_Algebra.Computational_Algebra"
"HOL-Number_Theory.Number_Theory"
begin
theorem mathd_algebra_224:
"card { n :: nat. sqrt n < 7 / 2 \<and> 2 < sqrt n} = 8"
sorry
end