In 2020, Hang buys a new shoe. Currently you have money available but not enough to buy. So you plan to save money from February 1, 2020 to March 31, 2020. In April, Hang invited An to the store to buy shoes. After buying, Hang bought 2 more cups of milk tea for 30000 VND a cup and had 60000 VND left over. Let y (dong) be the amount of money Hang has available, x (dong) is the amount of money you save from February 1 to March 31, 2020. a) Make a function y over x knowing that the shoes you bought cost 680000
b) Knowing how much money Hang has available is her grandparents' lucky money for Hang's sisters. Grandparents and grandparents spent lucky money for 2 sisters is 360,000 VND, the amount is divided according to the age ratio. Asking how much money Hang has to save every day to have money to buy shoes. Know Hang is 15 years old and Hang's younger brother is 12 years old