<math> <apply><forall/> <bvar><ci>x</ci></bvar><bvar><ci>f</ci></bvar><bvar><ci>g</ci></bvar> <apply><eq/> <apply><apply><compose/><ci>f</ci><ci>g</ci></apply> <ci>x</ci> </apply> <apply><ci>f</ci><apply><ci>g</ci><ci>x</ci></apply></apply> </apply> </apply> </math>