林先生是该店的会员。他花了 $3115.20 购买了 3 台笔记本电脑。

1. Find the price of a laptop before discount (from part a)

Let the original price of a laptop be $x$.
For a member buying 3 laptops:
1st laptop: $0.9x$
2nd laptop: $0.75x$
3rd laptop: $0.75x$
Total paid = $0.9x + 0.75x + 0.75x = 2.4x$
$2.4x = 3115.20$
$x = \frac{3115.20}{2.4} = 1300$

2. Calculate the price paid by a non-member for 1 laptop

Non-member discount is 5%.
Price paid = $1300 \times (1 - 0.05) = 1300 \times 0.95 = 1235$