Acoin is flipped 10 times and lands on heads 8 times. what is the theoretical probability that the coin will land on tails on the next flip?

20%
50%
80%
100%

Hope  this helps but I think the answer is 20%.

The theoretical probability of a coin landing on tails on any flip regardless of whatever has happened prior is always 1/2.  Notice that you are asking about the probability of what happens on the next flip.  You are not asking for the probability of what occurs in 10 flips.