I would say that you cannot answer the question if you dont know either the X-value or Y-value. You need to know at least one of them to figure out the other.
Total money Marcus has = $28
Money spent to buy a notebook = $3.75
Money left now = 
Money needed to be saved = $11.25
So, the amount of money Marcus can spend = 
Cost of a packet of chips = $1.30
The inequality to determine the maximum number of chips he can buy is:
Let the number of chips Marcus can buy = x
As he cannot spend more than $13 to buy chips so equation becomes:

Solving this we get

Hence, Marcus can buy a maximum of 10 packs of chips and save $11.25
Answer:
76,800
Step-by-step explanation:
This is because 808 is closer to 800
X goes by 1s
And y goes by 3s