What is the adult to child ratio of 8: 5 if 390 attend how many are children

Given f(x)= 9x+1 and g(x)=x^3, choose the expression (f*g)(x)

The probability that a student graduating from suburban state university has student loans to pay off after graduation is .60. if two students are randomly selected from this university, what is the probability that neither of them has student loans to pay off after graduation?

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.