a) 5−2−31=15−6−155=15−11;
b) 21.73+21.74=21.(73+74)=21.1=21;
c) 65−(31+21):20%=65−(62+63)⋅20%
=65−65⋅51=65−61=64=32;
d) 173.296−173.2935+2022173=173⋅(296−2935)+2022173
=173⋅(29−29)+2022173=173⋅(−1)+2022173
=17−3+2022173=2022.