Showing a language is decidable
123598
Showing the set of DFAs that accept nonempty languages is decidable
15842
Lambda calculus expression reduction
56644
Trying to figure what language this PDA (pushdown automata) accepts
136362
Marking plural of code words
107975
Show that the class of regular languages is closed under shuffle
148028
Are there statements that are undecidable but not provably undecidable
140682
Proving a property of a Logic Formal Language
51669
Stop guessing/auto-detecting a language when you KNOW it will be incorrect
17966
Representing the statement using Quantifiers
46698
Showing a set is closed under inverses
61471
Decidability of the Riemann Hypothesis vs. the Goldbach Conjecture
21254
Formal language: Proving the reverse operation on a word through induction
4383
Finitely generated monoids - how to show that there is not first order set axiomatizing them.
113342
Confusion of the decidability of $(N,s)$
18968
Converting English into first order predicate logic
111349
Finite automaton that recognizes the empty language $\emptyset$
124315
Drawing automata for languages