Question

If the two coins are tossed which is not a possible value of the random variable for the number of tails

Answer 1

Let's denote H - heads, T - tails.

Sample space S is all possible outcomes.

$$S = \{HH, TH, HT, TT\}$$

Let $t$ be the random variables representing the number of tails that occur. The possible values of $t$ are $0,1,2.$

Then 3 is not a possible value of the random variable for the number of tails.

All real numbers except the values $0,1,2$  are not a possible value of the random variable for the number of tails.