Уравнение: 9: (4/5-5/4) / 7: (3/4-4/3) = x/5: (3/2-2/3)

9 : (4/5 - 5/4) / 7 : (3/4 - 4/3) = x/5 : (3/2 - 2/3);

9 : ((4 * 4 - 5 * 5) / 20) / 7 : ((3 * 3 - 4 * 4) / 12) = x/5 : ((3 * 3 - 2 * 2) / 6);

9 : ((16 - 25) / 20) / 7 : ((9 - 16) / 12) = x/5 : ((9 - 4) / 6);

9 : ( - 9/20) / 7 : ( - 7/12) = x/5 : (5/6);

9 * ( - 20/9) / 7 * ( - 12/7) = x/5 * 6/5;

- 20 / ( - 12) = x/5 * 6/5;

20/12 = (x * 6) / (5 * 5);

20/12 = (x * 6) / (5 * 5);

20/12 = (6 * x) / 25;

(4 * 5) / (4 * 3) = (6 * x) / 25;

5/3 = (6 * x) / 25;

5 * 25 = 3 * (6 * x);

125 = 18 * x;

x = 125 : 18;

x = 6 17/18.

Ответ: 6 17/18.