387:x=513:57
387:x=9
x=387:9
x=43
---------------------------------------
387:43=513:57
9=9
a:6=54*8
a:6=432
a=432*6
a=2592
---------------------------------
2592:6=54*8
432=432.
3210-k=665:7
3210-k=95
k=3210-95
k=3115
---------------------------------------
3210-k=665:7
95=95