1/2
If there is one head and one tail for each coin the probability would be 1/2. There are two terms with only one answer 1/2.
OR
If you are asking for the end result of heads and the coins you would get 2/3. There are three terms with only one answer. 2/3.
4x+1=2x+7
-1 -1
4x=2x+6
-2x -2x
2x=6
2x/2- 6/2
X=3