Chen buys 4 notebooks and 3 pens for $17.50 . Liu buys 2 notebooks and 5 pens for $14. Form a pair of simultaneous equations and solve them to find the cost of a notebook and the cost of a pen.
Show your working.

Darcy deposited $390 into a savings account. as long as the account balance remains at or above $150, she does not have to pay a service fee for the account. for how many months can she withdraw $40 a month without having to pay service fees? a) 3 b) 5 c) 6 d) 9