Предмет: Математика, автор: ПростойЧеловекДаша

Помогите пожалуйста, №215, объясните как решить

Приложения:

Ответы

Автор ответа: vika2527
1

Ответ:

а) 7

б) 8

Пошаговое объяснение:

а) Перекрестное умножение:

3×5x=15х

5×21=105

15х=105(разделяем обо части на 15)

х=7

б) Перекрестное умножение

5×4х=20х

8×20=160

20х=160(разделяем обо части на 20)

х=8

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