If 3<x<8 and 5<y<11, which of the following represents all the possilbe values of xy??

Consider all of the possible values ranging from the lowest value of x on its interval multiplied with the lowest value of y on its interval, (3*5 = 15) up to the largest value of x multiplied with the largest value of y (8*11 = 88). This will give you an interval of possible values for xy. Since your original intervals are open, that is they do not include the "smallest" and "largest" values, your final interval of possible values for xy will also be open.