Let x be the original cost of the table. Then Zuzu sold it at the price (1-0.2)*x = 0.8x. In the second (hypothetical) case Zuzu would sold it at the price (1+0.5)x = 1.05x. The problem says that 0.8x + 800 = 1.05x. Now you solve this equation in ONE LINE 800 = 1.05x - 0.8x ====> 800 = 0.25x ====> x == 3200. ANSWER