А)1/4+3/8×1 2/3 = 1/4+ 3/8• (3•1+2)/3= 1/4+ 3/8• 5/3= (Три и три сокращаем) 1/4+ 1/8• 5/1= 1/4+ 5/8= (1•2)/(4•2)+ 5/8= 2/8+ 5/8= 7/8. ____________________________________________________________________
в)3 1/6×1 1/2-4= (6•3+1)/6• (2•1+1)/2 -4= 19/6• 3/2-4= (6 и 3 сокращаем на три) 19/2• 1/2- 4= 19/4- 4= 19/4- (4•4)/4= 19/4- 16/4= 3/4.