1) х - 5/2 = 9 - х/3
6х - 15 = 54 - 2х
6х + 2х = 54 +15
8х = 69
х = 69/8
2) 8 +х/7 = 3х - 5/6,5
8*91 + х*13 = 3х*91 - 5* 14
728 + 13х = 273х - 70
13х - 273х = - 70 - 728
-260х = -798
х = 798/260
х = 399/130 = 3 9/130
3) 7х + 9/2,5 = 5х - 2/6
7х*30 + 9 * 12 = 5х * 30 - 2*5
210х + 108 = 150х - 15
210х - 150х = - 108 - 15
60х = - 123
х = - 123/60 = - 41/20
х = - 2 1/20
4) 0,6/х - 3 = 2,1/х + 2
0,6 - 3*х = 2,1 + 2*х
0,6 - 2,1 = 2х + 3х
- 1,5 = 5х
х = -1,5 /5
х = - 0,3