1) b-5//14 при b= 5 1//7 2) (7 1//10z +z): 0,4=4,5

1) 5 1/7 - 5/14 = (5 * 7 + 1)/7 - 5/14 = (35 + 1)/7 - 5/14 = 36/7 - 5/14 = 2 * 36/14 - 5/14 = (72 - 5)/14 = 67/14;

Ответ: 67/14.

2) (7 1/10 * z + z) : 0,4 = 4,5;

((7 * 10 + 1)/10 * z + z) : 4/10 = 45/10;

(71/10 * z + 10/10 * z) * 10/4 = 9/2;

81/10 * z * 10/4 = 9/2;

z = 9/2 * 4/10 * 10/81 = (9 * 4 * 10)/(2 * 10 * 81) = 2/9;

Ответ: z = 2/9.