19 * (39 - 2х) = 703
39 - 2х = 703 : 19
39 - 2х = 37
2х = 39 - 37
2х = 2
х = 1
--------------------------------
19 * (39 - 2 * 1) = 703
19 * (39 - 2) = 703
19 * 37 = 703
703 = 703
2 * (2х + 3х) = 20
2 * 5х = 20
5х = 20 : 2
5х = 10
х = 2
--------------------------------
2 * (2 * 2 + 3 * 2) = 20
2 * (4 + 6) = 20
2 * 10 = 20
20 = 20
12 * (х + 9х) = 1200
12 * 10х = 1200
10х = 1200 : 12
10х = 100
х = 10
-------------------------------------
12 * (10 + 9 * 10) = 1200
12 * (10 + 90) = 1200
12 * 100 = 1200
1200 = 1200