№ 1
2х + 1 2,5
-------- = ---------
1,3 0,65
0,65 * (2х + 1) = 1,3 * 2,5
1,3х + 0,65 = 3,25
1,3х = 3,25 - 0,65
1,3х = 2,6
х = 2,6 : 1,3
х = 2
№ 2
3,25 13
----------- = ----------
4х - 1,9 0,4
13 * (4х - 1,9) = 0,4 * 3,25
52х - 24,7 = 1,3
52х = 1,3 + 24,7
52х = 26
х = 26 : 52
х = 0,5
№ 3
2,7 1 1/5
----- = -----------
9 3х + 1
2,7 * (3х + 1) = 9 * 1 1/5
8,1х + 2,7 = 9 * 6/5
8,1х + 2,7 = 54/5
8,1х = 54/5 - 2,7
8,1х = 54/5 - 2 7/10
8,1х = 54/5 - 27/10
8,1х = 108/10 - 27/10
8,1х = 81/10
8,1х = 8,1
х = 8,1 : 8,1
х = 1
№ 4
1 4/5 7,2
--------- = --------------
2,5 6х + 1
1 4/5 * (6х + 1) = 7,2 * 2,5
9/5 * (6х + 1) = 18
54/5х + 9/5 = 18
54/5х = 18 - 9/5
54/5х = 17 5/5 - 9/5
54/5х = 16 10/5 - 9/5
54/5х = 16 1/5
х = 16 1/5 : 54/5
х = 81/5 * 5/54
х = 81/54
х = 9/6 = 3/2 = 1,5