5x - 8/5 = 4
=> 5x = 4 + 8/5
=> 5x = 20/5 + 8/5
=> 5x = 28/5
=> x = 28/5

4/45 - 2 31/45 = 4/45 - (2 + 31/45)
= 4/45 - (90/45 + 31/45)
= 4/45 - 121/45
= (4 - 121)/45
= -117/45

Ответ: x = 28/5, -117/45