3.68(4,5),3.70(3,4),3.72(2,3)

3.68

4) у = 1,5х - 5

0 = 1,5х -5

-1,5х = -5

х = , или 3

5) у = -х + 4

0 = -х + 4

0 = -2х + 12

2х = 12

х = 6