(430+х)-80=720
430+x-80=720
x=720-430+80
x=370
(430+370)-80=720
720=720
400-(х-300)=200
400-x+300=200
x=400+300-200
x=500
400-(500-300)=200
200=200
1)430+х-80=720
х=720+80-430
х=370
2)400-х+300=200
700-200=х
х=500
