20*k=4200
k=4200:20
k=210.
m*900=63000
m=63000:900
m=70.
2400:n=120
n=2400:120
n=20.
p:35=70000
p=70000*35
p=2450000.
210+x=6310
x=6310-210
x=6100.
y+795=42995
y=42995-795
y=42200.
38420-z=6420
z=38420-6420
z=32000.
w-6159=16659
w=16659+6159
w=22818.