Aproper unbiased coin was tossed 10 times for 3 trials, giving tthhthtthh, , and ththhhttht (t = tails; h = heads). what is the difference between the theoretical and experimental probabilities of getting heads?

Theoretical probability (head or tail) = 1/2(10) = 50: 50
experimental probabilities: 
1st trial: TTHHTHTTHH  P(H)= 5 , P(T) = 5   i.e. 50:50
2nd trial: P(H) =5 , P(T) = 5   i.e 50 50
3rd trial: THTHHHTTHT  P(H) =5 , P(T) = 5  i.e. 50 50

These three trials show that , at least in this case, there is no difference between the theoretical probability and the experimental probabilty   

 
 

20y5 times 2 is 1010 times -2 is -20, plus y