Б-а=в
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<span>12х+15=5х-19</span>
<span>12х-5х=-19-15</span>
7х=-34
х=-34/7
х=-4 целых 6/7
Ответ:-4 целых 6/7
<span>25-3b=9-5b</span>
<span>-3b+5b=9-25</span>
<span>2b=-16</span>
<span>b=-16:2</span>
b=-8
Ответ:-8
Х * 215 - 4936 = 63 219
х * 215 = 63 219 + 4 936
х * 215 = 68 155
х = 68 155 : 215
х = 317
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317 * 215 - 4936 = 63 219
63 219 = 63 219
26176:(y×56-46856)=409
y×56-46856=26176:409
y×56-46856=64
y×56 =64 + 46856
y×56 = <span>46920
</span>y = <span>46920 : 56
</span>у = 837,8
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(y+3698):507=630
y+3698=630 х 507
y+3698=319410
у = 319410 - 3698
у = 319041
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42172-5×x=7152
-5×x=7152- <span>42172
</span>-5х = - 35020
х = - 35020: (-5)
х = 7004