1) /3х+1,8/=0 -опечатка!
2) 8/х=6/5
х*6=8*5
6х=40
х=40:6
х=406
х=203
х=6 23
3) х+3/12=4/3
х=43-312
х=1612-312
х=1312
х=1 112
4) 3х+16=9-10х
3х+10х=9-16
13х=-7
х=-7:13
х=-713
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=-2210*106
х=-226
х=-3 46
х=-3 23