Andrews–Curtis conjecture
In mathematics, the Andrews–Curtis conjecture states that every balanced presentation (i.e. a presentation with the same number of generators and relations) of the trivial group can be transformed into a trivial presentation by a sequence of Nielsen transformations on the relators together with conjugations of relators, named after James J. Andrews and Morton L. Curtis who proposed it in 1965.
Source: Wikipedia — Andrews–Curtis conjecture (CC BY-SA 4.0)