5. Решите уравнение: a) 6 * x + 2 * x + 30 = 70; б) 5 * (x + 2) + 10x = 100; в) 630 : (3x - 21) - 47 = 23; г) (8y - 65) : 7 + 39 = 64.

Решение:

1. \( 6x + 2x + 30 = 70 \)
   \( 8x = 70 - 30 \)
   \( 8x = 40 \)
   \( x = \frac{40}{8} \)
   \( x = 5 \)
2. \( 5(x + 2) + 10x = 100 \)
   \( 5x + 10 + 10x = 100 \)
   \( 15x = 100 - 10 \)
   \( 15x = 90 \)
   \( x = \frac{90}{15} \)
   \( x = 6 \)
3. \( 630 : (3x - 21) - 47 = 23 \)
   \( 630 : (3x - 21) = 23 + 47 \)
   \( 630 : (3x - 21) = 70 \)
   \( 3x - 21 = \frac{630}{70} \)
   \( 3x - 21 = 9 \)
   \( 3x = 9 + 21 \)
   \( 3x = 30 \)
   \( x = \frac{30}{3} \)
   \( x = 10 \)
4. \( (8y - 65) : 7 + 39 = 64 \)
   \( (8y - 65) : 7 = 64 - 39 \)
   \( (8y - 65) : 7 = 25 \)
   \( 8y - 65 = 25 \cdot 7 \)
   \( 8y - 65 = 175 \)
   \( 8y = 175 + 65 \)
   \( 8y = 240 \)
   \( y = \frac{240}{8} \)
   \( y = 30 \)

Ответ: a) 5; б) 6; в) 10; г) 30.