1) 12×17+35×13+17×23.
17 (12+23)+35×13.
17×35+35×13.
35 (17+13)=35×30=350×3=1050.
2) 41×80-25×41+55×29.
41(80-25)+55×29.
41×55+55×29.
55 (41+29)=55×70=550×7=3850.
3) 29×25+15×6+19×15
15 (6+19)+29×25.
15×25+29×25.
25 (15+29)=25×44=1100.
4) 26×18+17×26+14×35.
26(17+18)+14×35.
26×35+35×14.
35(26+14)=35×40=350×4=1400.