Вправа 820 алгебра Бевз гдз 7 клас

a) x – (3х – 5) = 9
x – 3x + 5 = 9
–2x = 4
x = 4 : (–2)
х = –2
–2 – 3(–2) + 5 = 9;
b) 12 – (5х + 4) = 13
12 – 5х – 4 = 13
–5х = 13 – 8
х = 5 : (–5)
х = –1
12 – 5(–1) – 4 = 13;

с) 6(2х – 1) = 18
3х – 6 = 27
3х = 33
х = 33 : 3
х = 11
3 • 11 – 6 = 27.

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