isabelle/valid/amc12b_2020_p5.thy (13 lines of code) (raw):
(*
Authors: Wenda Li
*)
theory amc12b_2020_p5 imports
Complex_Main
begin
theorem amc12b_2020_p5:
fixes a b :: nat
assumes "(5::real) / 8 * b - 2 / 3 * a = 7"
and "of_nat b - (5::real) / 8 * b - (a - 2 / 3 * a) = 7"
shows "a = 42"
sorry
end