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4x-7y=30
4x-5y=90
отнимем
-2у=-60
у=30
4x-150=90
4x=240
x=60
(60;30)
Y=7x-1 , при х=4
у=7×4-1=28-1=27
ответ: 27
4/10 * 1/3 = 4/30
5/6 * 12/10 = 60/60 = 1
4/30 / 1 = 4/30 = 2/15
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25/10 = 5/2
5/2 * 4/5= 20/10 = 2
16/10 = 8/5
8/5 * 3/4 = 24/20 = 6/5
2 / 6/5 = 2 * 5/6 = 10/6 = 5/3