Ответ:
Пошаговое объяснение:
а. (4 1/9 - а) + 8 5/9 = 9 2/9
4 1/9 - а = 9 2/9 - 8 5/9 = 83/9 - 77/9 = (83-77) / 9 = 6/9
а = 4 1/9 - 6/9 = 37/9 -6/9 = (37-6) / 9 = 31/9 = 3 4/9
проверка (4 1/9 - 3 4/9) + 8 5/9 = 9 2/9
б. 5 3/7 - (b - 2 1/7) = 2 4/7
b - 2 1/7 = 5 3/7 - 2 4/7 = 38/7 - 18/7 = 20/7
b = 20/7 + 2 1/7 = 20/7 + 15/7 = 35/7 = 5
проверка 5 3/7 - (5 - 2 1/7) = 2 4/7
в. 500 - 400 : (х + 43) = 495
400 : (х + 43) = 500 - 495 = 5
х + 43 = 400 : 5 = 80
х = 80 - 43 = 37
проверка 500 - 400 : (37 + 43) = 495
г. (270 : у - 12) * 70 = 1260
270 : у - 12 = 1260 : 70 = 18
270 : у = 18 + 12 = 30
у = 270 : 30 = 9
проверка (270 : 9 - 12) * 70 = 1260