[tex]a)\\23\cdot4=46\cdot2=92\\92\cdot4=184\cdot2=368\\235\cdot4=470\cdot2=940\\b)\\17\cdot6=34\cdot3=102\\29\cdot6=58\cdot3=174\\56\cdot6=112\cdot3=336[/tex]
[tex]a)\\27\cdot12=270+54=324\\62\cdot14=620+248=868\\35\cdot15=350+175=525\\b)\\31\cdot22=620+62=682\\25\cdot24=500+100=600\\13\cdot31=390+13=403[/tex]