(х+8):4=3, х+8=3*4,х+8=12, х=12-8, х=4
(30-х)-7=9, 30-х=9+7, 30-х=16, х=30-16, х=14
(19+х)-8=16, 19+х=16+8, 19+х=24, х=24-19, х=5
(х-7)+12=25, х-7=25-12, х-7=13, х=13+12,х=20
(х+8):4=3, х+8=3*4,х+8=12, х=12-8, х=4
(30-х)-7=9, 30-х=9+7, 30-х=16, х=30-16, х=14
(19+х)-8=16, 19+х=16+8, 19+х=24, х=24-19, х=5
(х-7)+12=25, х-7=25-12, х-7=13, х=13+12,х=20