A) 4/7*4 3/8= 1/7*4 3/2= 1/7*2*3=6/7
б)7/8*16/21-0.3:1*4/5=2/3 -0.3*0.8= 2/3 -0.24=2/3 - 24/100= 2/3 - 6/25= (50-18)/(75)=32/75
в)2 5/8:(6:3 3/7)+5 1/6=5/4:(18/7*1/3)+5/6=5/4:6/7+5/6=35/24+5/6=(35+20)/(24)=55/24
г)(7 1/12-4 2/3:3 1/3=
71/12-5*2/3*1/3*1/3=71/12*4*2/27=71/12-8/27= (639-32)/(108)=607/108
как понял, так решил!.