let p, q, r be Element of CQC-WFF ; :: thesis: (p => q) => (('not' (q '&' r)) => ('not' (p '&' r))) is valid
A1: (p => q) => (('not' (q '&' r)) => ('not' (p '&' r))) in TAUT by Def1, Th76;
thus (p => q) => (('not' (q '&' r)) => ('not' (p '&' r))) is valid by A1, Lm13; :: thesis: verum