Для каких значений х выполняется равенство: 4)2,6(х)=13; 5)3/8(х)=3/4; 7)0,7(-х)=2,8; 8)2/3(х)=4; 9)1,2(х)=4,27

4) 2,6 * х = 13          5) 3/8 * х = 3/4                7) 0,7 * (- х) = 2,8

х = 13 : 2,6               х = 3/4 : 3/8                     (- х) = 2,8 : 0,7

х = 5                         х = 3/4 * 8/3                     (- х) = 4

Проверка:                х = 8/4                              х = - 4

2,6 * 5 = 13               х = 2                                Проверка:

                                 Проверка:                       0,7 * (-(-4)) = 0,7 * 4 = 2,8

                                 3/8 * 2 = 6/8 = 3/4 

8) 2/3  * х = 4                                  9) 1,2 * х = 4,27

х = 4 : 2/3                                        х = 4,27 : 1,2

х = 4 * 3/2                                       х = 427/120

х = 12/2                                           х = 3 67/120

х = 6                                                Проверка: 12/10 * 427/120 = 427/100 = 4,27

Проверка: 2/3 * 6 = 12/3 = 4