А) (3/4 + 5/6) * 6 = 9 1/2
выражением:
(3/4 + 5/6) * 6 = (9/12 + 10/12) * 6 = 19/12 * 6/1 = 19/2 = 9 1/2
по действиям:
1) 3/4 + 5/6 = 9/12 + 10/12 = 19/12 = 1 7/12
2) 1 7/12 * 6 = 19/12 * 6/1 = (19*1)/(2*1) = 19/2 = 9 1/2
б) (6 1/4 - 2/3) : (3 1/2 + 1 7/8 ) = 1 5/129
выражением:
(6 1/4 - 2/3) : (3 1/2 + 1 7/8) = (6 3/12 - 8/12) : (3 4/8 + 1 7/8)=
= 5 7/12 : 5 3/8 = 67/12 * 8/43 = (67*2)/(3*43) = 134/129 =
= 1 5/129
по действиям:
1) 6 1/4 - 2/3 = 6 3/12 - 8/12 = 5 15/12 - 8/12 = 5 7/12
2) 3 1/2 + 1 7/8 = 3 4/8 + 1 7/8 = (3+1) + 11/8 =
= 4 + 1 3/8 = 5 3/8
3) 5 7/12 : 5 3/8 = 67/12 : 43/8 = (67*8)/(12*43) =
= (67*2)/ (3*43) = 134/129 = 1 5/129