SOLUTION: Suppose x coins are tossed. Write an expression to represent the number of possible outcomes

If 1 coin is tossed there would be 2 possible outcomes, (Head or Tail).
Notice that the number of ways is 2 or 21.

If 2 coins are tossed there are 2 possible outcomes for the 1st coin. 
Then for each of those 2 possible outcomes for the 1st coin, there are
2 possible otcomes for the 2nd coin. That's 2·2 or 4 ways. Notice that 
the number of ways for 2 coins is 2·2 or 22.

If 3 coins are tossed there are 2 possible outcomes for the 1st coin. 
Then for each of those 2 possible outcomes for the 1st coin, there are
2 possible otcomes for the 2nd coin. That's 2·2 or 4 ways for the first
two coins. Then for each of those 4 possible outcomes for the 1st coin, 
there are 2 possible otcomes for the 3rd coin. That's 2·2·2 or 4·2 or 
8 ways for the three coins.  Notice that the number of ways for 3 coins 
is 2·2·2 or 23.

Since 
1. The number of ways for 1 coin is 21 and
2. The number of ways for 2 coins is 22 and
3. The number of ways for 3 coins is 23.
4.
...

So we can generalize and say:

x. The number of ways for x coins is 2x.

Edwin