5) 2/3x=-3/8
16х=-9
х=-9/16
6)40,5:x=4
х=40,5:4
х=10,125
7)-32/63:x=8/21
-32/63*1/х=8/21
63х*8=-32*21
504х=-672
х=-1 21/63
х=-1 1/3
проверка
-32/63:(-84/63)=8/21
(32*63)/(63*84)=8/21
32/84=8/21
8/21=8/21
8)x:2/7=-1,4
х*7/2=-1 4/10
7х/2=-14/10
7х/2=-7/5
35х=-14
х=-14/35
х=-2/5