2,3z+4 1/2z-1 4/5-z=25

2,3z + 4 1/2z - 1 4/5 - z = 25;

23/10z + 9/2z - 9/5 - z = 25;

23/10z + 45/10z - z = 25 + 9/5;

68/10z - z = 125/5 + 9/5;

68/10z - 10/10z = 134/5;

58/10z = 134/5;

z = 134/5 : 58/10;

z = 134/5 * 10/58;

z = 134/29 = 4 18/29.

Проверка:

2,3 * 4 18/29 + 4 1/2 * 4 18/29 - 1 4/5 - 4 18/29 = 25;

23/10 * 134/29 + 9/2 * 134/29 - 9/5 - 134/29;

1541/145 + 603/29 - 9/5 - 134/29 = 25;

1541/145 + 3015/145 - 261/145 - 670/145 = 25;

4556/145 - 261/145 - 670/145 = 25;

4295/145 - 670/145 = 25;

3625/145 = 25;

25 = 25.

Ответ: z = 134/29 = 4 18/29.