Ответ:
Пошаговое объяснение:
78=1, 2, 3, 6, 13, 26, 39, 78
80=1, 2, 4, 5, 8, 10, 16, 20, 40, 80
81=1, 3, 9, 27, 81
82=1, 2, 41, 82
84=1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84
85=1, 5, 17, 85
87=1, 3, 29, 87
4x-1=2×( x+3)
4x-1=2x+6
4x-2x=6+1
2x=7
X=7 : 2
X=7/2
X=3 1/2=3,5
Удачи))