1) (41a-39a)47=3384
1927a-1833a=3384
94a=3384
a=3384/94
a=36
2) (500b-497b):85=99
500b-497b=99*85
3b=8415
b=8415/3
b=2805
3) 1050:(17x+8x)=21
1050=21(17x+8x)
1050=357x+168x
525x=1050
x=1050/525
x=2
4) 2244:(111z-9z)=22
2244=22(111z-9z)
2244=2442z-198z
2244z=2244
z=2244/2244
z=1