1) 69 - 4Z = 75 : 15
69 - 4Z = 5
4Z = 69 - 5
4Z = 64
Z = 64 : 4
Z = 16
.....................................................................................
2) 105 - 3Z = 1998 : 37
105 - 3Z = 54
3Z = 105 - 54
3Z = 51
Z = 51 : 3
Z = 17
....................................................................................
3) 7Z - 41 = 2576 : 28
7Z - 41 = 92
7Z = 92 + 41
7Z = 133
Z = 133 : 7
Z = 19