16. (500 - k : 4) \(\cdot\) 7 = 2940

Решение:

1. \[ (500 - k : 4) \cdot 7 = 2940 \]
2. \[ 500 - k : 4 = 2940 : 7 \]
3. \[ 500 - k : 4 = 420 \]
4. \[ k : 4 = 500 - 420 \]
5. \[ k : 4 = 80 \]
6. \[ k = 80 \times 4 \]
7. \[ k = 320 \]

Ответ: k = 320