20/7
Пошаговое объяснение:
-3/5х +1/4х + 4/7 = -3/7
12/20х - 5/20х = 4/7 + 3/7
7/20х = 1
х = 20/7
проверка
-3/5 * 20/7 + 1/4 * 20/7 + 4/7 = -3/7
-60/35 + 20/28 + 4/7 = -3/7
-12/7 + 5/7 + 4/7 = -3/7
-3/7 = -3/7
