pomagite pojaluysta N6

x+120=45*6
x+120=270
x=270-120
x=150

y*20=450+120+130
y*20=700
y=700/20
y=35


75/y=800-725
75/y= 75
y=75/75
y=1

450+a=570+430
450+a=1000
a=1000-450
a=550