24. 21/49 = x/7

Решение:

1. \[ \frac{21}{49} = \frac{x}{7} \]
2. \[ x = \frac{21 \times 7}{49} \]
3. \[ x = \frac{21}{7} \]
4. \[ x = 3 \]

Ответ: x = 3