Nixplay is currently running 30% off all frames, which is the main deal on this page and is best for shoppers buying a frame that costs several hundred dollars. The 30% off sale applies site wide to selected frames for a limited time, so it is the natural starting point for most carts. The other offers to check are the up to $90 off deals, the specific $50 off the 15.6" HD touch screen, and free shipping.
If you are buying an expensive frame over $300: Use the 30% off all frames. For example, on a $400 order the 30% off takes 30% (percent 30%) off, leaving $280, so you save $120. This beats a flat $90 saving on the same item.
If your frame costs less than $300: The up to $90 off promotion can save more, provided the model you want is one of the selected items that carry the fixed discount. For example, on a $250 frame the up to $90 off deal saves $90 (fixed 90%), leaving $160, so you save $90. On that $250 price the $90 fixed discount is larger than the 30% off, which would save $75.
If you are buying the 15.6" HD touch screen Big Classic: Use the $50 off Big Classic 15.6" HD touch screen deal, since the product page already reflects the discount. For example, if the listed regular price is $299, the $50 off (fixed 50) reduces the price to $249, so you save $50. The 30% sale might not apply to that specific listing if the product is only in the fixed price promotion, so confirm the product page price.
If the frame is in a site wide frame sale that shows a lower percentage (up to 23% off): The 30% off all frames is larger than up to 23% off, so prefer the 30% deal when it applies. If an item is only included in the up to 23% event and not in the 30% event, use the percentage shown on its product page.
If you care about shipping cost: Free shipping applies to purchases under the listed shipping and delivery offer, so you do not need to add delivery to your calculations for any basket that qualifies for that free shipping condition.
To pick between the applicable offers for one basket, compare the final totals. For a single product, calculate 30% off the original price and compare that result to any flat dollar discount shown on the product page (for example $90 off or $50 off). Take whichever leaves the lower total. The $50 Big Classic saving is a product specific price shown on its page and will already be reflected at checkout, while the other discounts apply only to selected products or while stock lasts.