Final answer:
Zach needs to save $90 more to buy the iPod.
Step-by-step explanation:
To find out how much more Zach needs to save to buy the iPod, we need to subtract the amount he has saved from the cost of the iPod. Zach has saved $55 and the cost of the iPods starts at $145. To find the difference, we subtract $55 from $145.
$145 - $55 = $90
Therefore, Zach needs to save $90 more to buy the iPod.