Since, rolling a die and tossing a coin are independent events, the sample space of both events is the product of the outcomes for each event, i.e 6 × 2 = 12.
You can check that here:
roll a die toss a coin 1 head 1 tail 2 head 2 tail 3 head 3 tail 4 head 4 tail 5 head 5 tail 6 head 6 tail
So, as you see for each outcome of the event roll a die there are two different possible different outcomes for the event toss a coin; since there are 6 different outcomes for the die, the total number of possibilities is 6 × 2 = 12
