Решение:
a) $$18\frac{2}{17} - (3\frac{5}{17} + x) = 5\frac{9}{17}$$
$$18\frac{2}{17} - 3\frac{5}{17} - x = 5\frac{9}{17}$$
$$15\frac{-3}{17} - x = 5\frac{9}{17}$$
$$14\frac{14}{17} - x = 5\frac{9}{17}$$
$$x = 14\frac{14}{17} - 5\frac{9}{17}$$
$$x = 9\frac{5}{17}$$
Ответ: $$9\frac{5}{17}$$
б) 2,7x - 1,84x + 5,87 = 8,88
0,86x + 5,87 = 8,88
0,86x = 8,88 - 5,87
0,86x = 3,01
x = 3,01 / 0,86
x = 3,5
Ответ: 3,5