A×(B+C)=A×B+A×C 例:5×(6+8) =5×6+5×8 =30+40 =70 A×B+A×C=A×(B+C) 例:5×17+5×3 =5×(17+3) =5×20 =100 A×(B-C)=A×B-A×C 例:5×(8-6) =5×8-5×6 =40-30 =10