Okay, here we have this:
Considering the provided information, we are going to calculate the requested value, so we obtain the following:
Then we will substitute in the following formula:
Students who play soccer=Number of students*(Probability that they play soccer)
Replacing:
Students who play soccer=300*(12/25)
Students who play soccer=3600/25
Students who play soccer=144
Finally we obtain that 144 students would we expect to play soccer, based on Sean's experiment.