Salutare !
a) = {16+7[31+10(3²+3)-49]}:73
= {16+7[31+10(9+3)-49]}:73
= [16+7(31+10×12-49)]:73
= [16+7(31+120-49)]:73
= (16+7×102):73
= (16+714):73
= 730:73
= 10
