We are all very careless in our use of the word percent. When we say percent we should indicate percent of what. If your client wants to mark up what the item costs them by 25% then they would add 25% of what it costs them. 25% of $35.95 is
0.25 $35.95 = $8.99
so if your clients sells the item for $35.95 + $8.99 = $44.94 then their profit is 25% of what the item cost them.
On the other hand if you client wants to make a profit of 25% of what they sell the item for then they should charge $39.95/(1 - 0.25) = $53.27.
I hope this helps,