Answer:
y-x = -1
Explanation:
Given the two dataset;
(8,x,4,1) and (9,y,5,2)
Since they are already arranged in descending order;
The median for the first dataset is;
M1 = (x+4)/2
The median for the second dataset is;
M2 = (y+5)/2
The median is equal;
M1 = M2
(x+4)/2 = (y+5)/2
x+4 = y+5
Collecting the like terms;
4-5 = y-x
y-x = -1