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