10*x=8*25
x=200/10
x=20
------
10*20=8*25
200=200
x/20=4800/80
x=20*60
x=1200
----------
1200/20=4800/80
60=60
(x-380)*50=2000
x-380=2000/50
x-380=64
x=380+64
x=444
--------
(444-380)*50=2000
2000=2000
(x+8)/70=4
x+8=70*4
x+8=280
x=280-8
x=212
--------
(212+8)/70=4
4=4
640/(25-x)=40
25-x=640/40
25-x=16
x=25-16
x=9
-----
640/(25-9)=40
40=40
2700/(x-12)=90
x-12=2700/90
x-12=30
x=12+30
x=42
------
2700/(42-12)=90
90=90