Now I'm saying everything is right, but here you go.
1. Part: 12, Percent: 20%, Whole: 60
2. Part: 15, Percent: 30%, Whole: 50
3. Part: 24, Percent: 75%, Whole: 32
All I've been doing is taking the part and dividing it by the percentage (written as a decimal) you turn the percentage into a decimal by moving the point 2 spaces left.
I've told you everything I've done to find the first 3. I'm sure you can figure out the rest. Hope the instructions helped!