The median of the set of values a, b, a+2b, a-3b, ab and 3b where a<b

Least value = a - 3b (Negative)

We can see a - 3b < a < b (Given a < b)

Between a + 2b & 3b ; 3b is higher (since a < b)

To decide between a + 2b & ab;
Assume least value of a = 8/3 (approx)
--> 8/3 + 2b & 8/3b
--> 8/3 + 2b & 2/3b + 2b
--> Since b > 4, 2/3b is always greater than 2*4/3 = 8/3
--> ab > a + 2b

In ascending order,
Possible set 1 = {a - 3b, a, b, a + 2b, ab, 3b}
Possible set 2 = {a - 3b, a, b, a + 2b, 3b, ab}

Note: We can also see the options DO NOT have 'ab' in them. so, we can assume the above order

From both the possible sets, Median = average of 3rd & 4th term
--> Median = (b + a + 2b)/2 = (a + 3b)/2

IMO Option B

Alternate Method:

Assume a = 3, b = 5

a, b, a + 2b, a - 3b, ab and 3b
--> 3, 5, 3 + 2*5, 3 - 3*5, 3*5, 3*5
--> 3, 5, 13, -12, 15, 15
--> -12, 3, 5, 13, 15, 15 (Ascending order)

Median = (5 + 13)/2 = 9

Only Option B satisfies!

Pls Hit Kudos if you like the solution