Ответ:

1) \(1.23x - 1.229x = 1.8\); \(0.001x = 1.8\); \(x = 1800\).

2) \(3.6y + 2.8y = 2.24\); \(6.4y = 2.24\); \(y = 0.35\).

3) \((x + 2.4) \cdot 0.18 = 61.2\); \(x + 2.4 = 61.2 : 0.18 = 340\); \(x = 340 - 2.4 = 337.6\).

Ответ: 1) \(x=1800\); 2) \(y=0,35\); 3) \(x=337,6\).