I think you solve it as so, someone should concur with me: start wih the lategest and use the data given on range and median.

range = largest - smallest

so 50-25 (range) = 25 , the smallest number . you have a set of 15 distinct numbers so one end is 50, the other end is 25, there is now way you can have a median of 25.

next number 43
43-25=18 . out of 15 numbers you have already picked two (the largest and smallest 43 and 18, and the median is 25, that is the 3rd number, then you have two fit 6 numbers netween the smallest ane the median, and 6 numbers between the median and the largest number 15-2-1=12 numbers left, 6 on each side of the median). looks like this is doable and you set looks like something like:

18,19,20,21,22,23,24,24, x1,x2,x3,x4,x5,x6,43

the answer is 43