Can price discounts from different sources 'stack'?

[SwampTing]

A player obtained the boon "the Kirin's debt repaid" (25% discount on 1 item purchase), and has the master of trade vanity (10% discount on an item purchase), and wants to use both on the purchase of the 1 item.

Can he stack both discounts? If so, are the discounts multiplied or added? Does he pay (90% x 75%) of the item's cost or 65% of the item's cost?

[BigNorseWolf]

As far as I know they stack.

65%

[dreadfury]

One of those coupons says cannot be combined with any other offer

[Cao Phen]

Bah, it is the buy "3 mutton meals and get the next 3 at 1/2 off" coupon...

[BigNorseWolf]

Damn bait and switch retailers!

[Samish Lakefinder]

Generally you do not add percentage discounts together before applying them, you apply them separately.
Discounted Price = Price x (1-.25) x (1-.1)= .675 Price = 67.5% Price