To solve these equations:

1) 321 - x = 45020
Subtract 321 from both sides:
-x = 45020 - 321
-x = 44699
Divide by -1 to solve for x:
x = -44699

2) 4 - x = -13
Add x to both sides:
4 = -13 + x
x = 4 + 13
x = 17

3) 6122 - y = -20050
Add y to both sides:
6122 = -20050 + y
y = 6122 + 20050
y = 26172

4) 3 - y = 72
Add y to both sides:
3 = 72 + y
y = 3 - 72
y = -69

Therefore, the solutions are:
1) x = -44699
2) x = 17
3) y = 26172
4) y = -69