How many different combinations are possible if a coin is tossed twice and a number cube is tossed once?

18 different combinations.

When a coin is tossed twice there are four possible outcomes, (H,H), (H,T), (T,H) and

(T,T) considering the order in which they appear (first or second). But if we are

talking of combinations of the two individual events, then the order in which they

come out is not considered. So for this case the number of combinations is three:

(H,H), (H,T) and (T,T).

For the case of tossing a die once there are six possible events.

The number of different combinations when tossing a coin twice and a die once is:

3x6 = 18 different combinations.