Answer:
1. C: three | V: y
2. C: 7 | V: p
3. C: four | V: x
4. C: sixteen, ten | V: k
5. C: two, twenty | V: g (I believe that's a "g" and not a "9" due to OCR scanning! and even logically that should be a letter to represent the variable so that the expression is correct)
6. C: six, twelve | V: p
7. C: twenty, eight | V: h
8. C: four, five | V: x
9. C: fifteen | V: f
10. C: two, forty | V: d