You can get the solutions of 1-3, 10 and 12, by multiplying the percent in a decimal form by the whole number. For example, for number 2: 0.25 * 120 = 30.
2. 30
3. 45
10. 60
12. 9
You can get the solutions of 4-6 and 11, by just reversing what you were doing earlier. For example, for number 4: 15 / 25 = 0.6 aka 60%.
4. 60%
5. 50%
6. 175%
11. 40%
For 7-9, you divide the second value by the decimal form of the first. For example, for 7: 15 / 0.20 = 70.
7. 75
8. 50
9. 13