1) /3х+1,8/=0 -опечатка!
2) 8/х=6/5
х*6=8*5
6х=40
х=40:6
х=40\6
х=20\3
х=6 2\3
3) х+3/12=4/3
х=4\3-3\12
х=16\12-3\12
х=13\12
х=1 1\12
4) 3х+16=9-10х
3х+10х=9-16
13х=-7
х=-7:13
х=-7\13
5) 0,6(х+1целая 2/3)=-1,2
0.6х+1=-1.2
0.6х=-1.2-1
0.6х=-2.2
х=-2.2:0.6
х=-22\10*10\6
х=-22\6
х=-3 4\6
х=-3 2\3