i need a list of data with the mode 15 min 5 median 10 max 20

Answer 1

Start with the min and max:

5............20

Insert the median (in the middle)
5......10......20

For mode =15, insert at least two 15 to the right of the median (10) and two different values to the left:

5 6 8 10 15 15 20

Finally check that all conditions are satisfied.