12÷13 1/3=12÷40/3=12×3/40=
=36/40=9/10 это число
(3a+2)/a+(2a-1)/2a=2|*2a
2(3a+2)+2a-1=4a
6a+4+2a-1-4a=0
4a+3=0
4a=-3
a=-3/4
x + 2y + 3z = 5
2x - y - z = 1
x + 3y + 4z = 6
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- x - 3y - 4z = - 6
- y - z = - 1
y = 1 - z
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2x - y - z = 1
2x = 1 + y + z
2x = 1 + 1 - z + z
2x = 2
x = 1
-------------------------
x + 2y + 3z = 5
1 + 2( 1 - z ) + 3z = 5
1 + 2 - 2z + 3z = 5
z = 5 - 3
z = 2
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y = 1 - z
y = 1 - 2
y = - 1
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ОТВЕТ x = 1 ; y = - 1 ; z = 2
(25+5)*6=180
50*6=300
100*6=600
200*6=1200
450*6=2700