87. Решите уравнение: a) \(3+a=\frac{5}{9}\); \(\text{ б)}\) x+2\(\frac{3}{7}\)=5\(\frac{1}{7}\).

Решение:

1. а) \( 3 + a = \frac{5}{9} \)
   \( a = \frac{5}{9} - 3 \)
   \( a = \frac{5}{9} - \frac{27}{9} \)
   \( a = \frac{5 - 27}{9} \)
   \( a = -\frac{22}{9} \)
   \( a = -2\frac{4}{9} \)
2. б) \( x + 2\frac{3}{7} = 5\frac{1}{7} \)
   \( x = 5\frac{1}{7} - 2\frac{3}{7} \)
   \( x = \frac{36}{7} - \frac{17}{7} \)
   \( x = \frac{36 - 17}{7} \)
   \( x = \frac{19}{7} \)
   \( x = 2\frac{5}{7} \)

Ответ: а) \(a = -2\frac{4}{9}\); б) \(x = 2\frac{5}{7}\).