х + (90+30) = 180
х + 120 = 180
х = 180 - 120
х = 60
_____
(х+90)+30 = 180
х + 90 = 180 - 30
х + 90 = 150
х = 150 - 90
х = 60
_____
(х-60) * 5 = 180
х-60 = 180 : 5
х-60 = 36
х = 36 + 60
х = 96
____
5 * х + 300 = 500
5 * х = 500 - 300
5 * х = 200
х= 200 : 5
х= 40
_____