0.7=7/10
4/7+7/10=40+49/70=1 19/70
14x-7=4x+8-4x+3;
14x+4x-4x=8+3+7;
14x=18;
X=18/14.
Vср=(5*60+3*100+4*75):(5+3+4)=(300+300+300):12=900:12=75км/ч
Y = 1/3x
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y = - 5
- 5 = 1/3x
x = - 5 : ( 1/3 )
x = - 15
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y = 1/6
1/6 = 1/3x
x = 1/6 : 1/3
x = 1/2
------------------
y = 0,2
0,2 = 1/3x
x = 1/5 : 1/3
x = 3/5
------------------
y = 0
0 = 1/3x
x = 0
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3 * 4 = 12 ( км )
Ответ 12 км