imi puteti explica va rog cum sa fac aceste exercitii?

3)60%=60/100=6/10=3/5
140%=140/100=14/10=7/5
4)40p/100=30=>p=100x30/40=75%
5)200p/100=300=>2p=300=>p=150%
6)70p/100=175=>7p/10=175=>p=170x10/7=250(numarul)
deci 20% va fi 20/100x250=1/5x250=50