а) 14x + 18x - 2.3 = 16.9
32x - 2.3 = 16.9
32x = 19.2
x = 19.2 / 32
x = 0.6

б) 20.4 / x + 6.3 = 18.3
20.4 / x = 18.3 - 6.3
20.4 / x = 12
20.4 = 12x
x = 20.4 / 12
x = 1.7

Ответ: а) x = 0.6, б) x = 1.7