Question 5602
In discount or price increase problems involving percentages, I always use the formula P ± Pc = N, where P is the original price, N is the new price (price after discount or price increase), and c is the percentage. Use + if it's a price increase. Use - if it's a price decrease. They will ALWAYS give you all but one of the values, and that value they didn't give you is what they want you to find.

In this case, P = $78.00, N = $104.00 and your quest now is to find c, the percentage. Since this is a price increase, we'll use the + instead of the -.

78.00 + 78.00c = 104.00
        78.00c = 26
             c = 0.33333 repeating, or 33 1/3 % price increase.