Jenna flips two pennies 105 times how many times can she expect those coins to come up heads

The more observations you make the closer and closer the experimental probability will approach the theoretical probability.  In this case the theoretical probability is:

P(HH)=(1/2)(1/2)=1/4

So in 105 trials one would expect to get two heads:

105(1/4)=26.25 times.