40-(23+7)=20 37 55 49 +6= 37 55 55 70 62 48 +23= 70 62 71
=14 82/90-4 27/90=10 55/90= 10 11/18
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А)
3/7 * (1/3+4/9) = 1/3
1) 1/3+4/9 = 3/9+4/9= 7/9
2) 3/7 * 7/9 = (3*7)/(7*9) = (1*1)/(1*3)=1/3
б)
4/5 - 1/4 : 5/6 =1/2
1) 1/4 : 5/6 = 1/4 * 6/5 = (1*6)/ (4*5) = (1*3)/ (2*5) =3/10
2) 4/5 - 3/10= 8/10-3/10= 5/10 = 1/2