1) 4/7 х (-5 5/6) - 5/62 х (-4 3/7) 2) (5 х+8) - (8 х+14) = 9 3) 2.7+3 у=9 (у-2.1

1) Вычислим выражение.

4/7 * (-5 5/6) - 5/62 * (-4 3/7) = - 4/7 * 5 5/6 + 5/62 * 4 3/7 = - 4/7 * (5 * 6 + 5) / 6 + 5/62 * (4 * 7 + 3) / 7 = - 4/7 * 35/6 + 5/62 * 31/7 = - (4 * 35) / (7 * 6) + (5 * 31) / (62 * 7) = - (2 * 35) / (7 * 3) + (5 * 1) / (2 * 7) = - (2 * 5) / (1 * 3) + 5/14 = - 10/3 + 5/14 = - 10 * 14/42 + 5 * 3/42 = - 140/42 + 15/42 = (-140 + 15) / 42 = - 125/42;

2) Найдем корень уравнения.

(5 * х + 8) - (8 * х + 14) = 9;

5 * x + 8 - 8 * x - 14 = 9;

(5 * x - 8 * x) + (8 - 14) = 9;

-3 * x - 6 = 9;

-3 * x = 9 + 6;

-3 * x = 15;

x = - 15/3;

x = - 5.

3) Найдем корень.

2.7 + 3 * у = 9 * (у - 2.1);

0,9 + y = 3 * (y - 2.1);

0.9 + y = 3 * y - 3 * 2.1;

0.9 + y = 3 * y - 6.3;

3 * y - y = 0.9 + 6.3;

2 * y = 7.2;

y = 7.2/2;

y = 3.6.