x:(50·4) = 3
x:200 = 3
x = 3·200
x = 600.
600:(50·4) = 600:200 = 3
c·(80·5) = 800
c·400 = 800
c = 800:400
c = 2
2·(80·5) = 2·400 = 800
5/x=0,2/3
0,2х=5*3
0,2х=15
х=15|:0,2
х=75