(х+155)-35=145
х+155=145+35
х+155=180
х=180-155
х=25
168-(98+z)=65
98+z=168-65
98+z=103
z=103-98
z=5
(853+у)-53=900
853+у=900+53
853+у=953
у=953-853
у=100
(s+275)-275=384
s+275=384+275
s+275=659
s=659-275
s=384
5х+2=18-3х
5х+3х=18-2
8х=16
х=2
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2/3х+0,5=-х
2/3х+х=-0,5
1.2/3х=-1/2
5/3х=-1/2
х=-1/2:5/3
х=-3/10
х=0,3
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(х+1)/3=2,8/4,2решаем пропорцию
(х+1)*4,2=3*2,8
4,2х=8,4-4,2
4,2х=4,2
х=1
1)2 7/8*1/5=23/40
2)1,625*1 1/3=13/6
4 1/4+5 3/4-2 1/7=4+5+1/4+3/4-2 1/7=9+4/4-2 1/7=9+1-2 1/7=10-2 1/7=
9+7/7-2 1/7=9-2+7/7-1/7=7+6/7=7 6/7