Water Vs Eno + Biscuits

If the cost of 2 chocolates and 3 biscuits is Rs 55 and that of 4 chocolates and 6 biscuits is Rs 110, then the costs of one chocolate and one biscuit are necessarily Rs 20 and Rs 5 respectively (True/False)

15 Pastries and 12 biscuit packets have been donated for a school fete. These are to be packed in several smaller identical boxes with the same number of pastries and biscuit packets in each. How many biscuit packets and how many pastries will each box contain?

In a bakery four types of biscuits are available. In how many ways a person can buy 10 biscuits if he decide to take at least one biscuit of each variety?