Ответ:

  1. \(47\cdot5=(40+7)\cdot5=200+35=235\); \(121\cdot4=(120+1)\cdot4=480+4=484\); \(89\cdot8=(90-1)\cdot8=720-8=712\).
  2. \(8\cdot36=8(30+6)=240+48=288\); \(6\cdot137=6(100+30+7)=600+180+42=822\); \(7\cdot39=7(40-1)=280-7=273\).
  3. \(7\cdot76=7(70+6)=490+42=532\); \(251\cdot7=(250+1)\cdot7=1750+7=1757\); \(9\cdot59=9(60-1)=540-9=531\).
  4. \(6\cdot92=6(90+2)=540+12=552\); \(18\cdot101=18(100+1)=1800+18=1818\); \(15\cdot29=15(30-1)=450-15=435\).