This question is from Exercise 15.1 of NCERT Class 10 Mathematics textbook. It tests the basic probability formula P(E) = Number of favourable outcomes / Total number of possible outcomes. The context shows similar solved examples where probability is calculated by counting favourable outcomes and total outcomes. For part (iii), the concept of complementary events is applied - P(not green) can be found either by subtracting green marbles from total or by adding probabilities of red and white marbles.