Make up a set of at least 12 numbers that have the following landmarks maximum 18 range 13 mode 7 and median 12

Answer 1

Start with maximum 18.
Range is 13, so minimum is 5.
Median is 12, so you'd be safe to put 12 (or 11 and 13) in the 6th and 7th place to get:
5 * * * * 12 12 * * * * 18, or
5 * * * * 11 13 * * * * 18.

All you need to do is to insert numbers so that the mode is 7. The mean is not specified, so you can put anything in the rest (but keeping the mode at 7).