6 дм = 0,6 м
................................
А)-1 2/5+(-2 1/5)=-3 3/5;///
б)-3/8+(-1/2)=-3/8-4/8=-7/8;///
в)-0,25+(-1/2)=-1/4-1/2=-1/4-2/4=-3/4
4500:100+300:10-10*(81:27+2)=45+30-10*5=75-50=25
10•3=30. 3•10. 30:3=10. 30:10
10•4=40. 4•10. 40:4=10. 40:10