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а) 21:8 3/4-9 9/10:6 3/5

б) 4 4/5:18+14/15*5/8

в) 4 5/8 + (3 1/6-1 3/4) * 10

г) 10 2/9-3 1/3: (2 5/21-1 2/3)

А) 21 : 8 3/4 - 9 9/10 : 6 3/5 =

= 21/1 * 4/35 - 99/10 * 5/33 =

= 12/5 - 3/2 = (24-15) / 10 = 9/10

б) 4 4/5 : 18 + 14/15 : 5/8 =

= 24/5 * 1/18 + 14/15 * 8/5 =

= (4*1) / (5*3) + 112/75 = 4/15 + 112/75=

= 20/75 + 112/75 = 132/75 = 44/25 = 1 19/25

в) 4 5/8 + (3 1/6 - 1 3/4) * 10 =

= 4 5/8 + (3 2/12 - 1 9/12) * 10 =

= 4 5/8 + 1 5/12 * 10 =

= 4 5/8 + 170/12 = 37/8 + 170/12=

= (111+340) / 24 = 451/24 = 18 19/24

г) 10 2/9 - 3 1/3 : (2 5/21 - 1 2/3) =

= 10 2/9 - 10/3 : (2 5/21 - 1 14/21) =

= 10 2/9 - 10/3 : 12/21 = 10 2/9 - 10/3 * 21/12 =

= 10 2/9 - (5 * 7) / (1*6) = 92/9 - 35/6 =

= (184 - 105) / 18 = 79/18 = 4 7/18