The event when the die lands on 6 on the second, third and fourth rolls but not on any of the other​ rolls can be represented by:

x1, x2, 6, 6, 6

where x1, x2 are numbers from 1 to 5

The total number of different rolls that can occur is:

6^5

The number of the events where the dice lands on 6 on the second, third and fourth rolls but not on any of the other​ rolls is:

5*5*1*1*1 = 5^2

P(x1, x2, 6, 6, 6) = 5^2/6^5

P(x1, x2, 6, 6, 6) = 0.0032

The probability is 0.0032.