1)6.7-x=3.9
х=3.9-6.7
х=-2.8
2)x+6.9=7.2
х=7.2-6.9
х=0.3
3)(x-5.4)+2.3=5.2
х-5.4=5.2-2.3
х=2.9+5.4
х=8.3
4)(9.1-x)-2.8=2.9
9.1-х=2.9+2.8
х=5.7-9.1
х=-3.4
1)6.7-x=3.9
х=3.9-6.7
х=-2.8
2)x+6.9=7.2
х=7.2-6.9
х=0.3
3)(x-5.4)+2.3=5.2
х-5.4=5.2-2.3
х=2.9+5.4
х=8.3
4)(9.1-x)-2.8=2.9
9.1-х=2.9+2.8
х=5.7-9.1
х=-3.4