If, during the first hour, 25 percent of the total displays were assembled, then 280(0.25) = 70 displays were assembled, leaving 280 - 70 = 210 displays remaining to be assembled. Since 40 percent of the remaining displays were assembled during the second hour, 0.40(210) = 84 displays were assembled during the second hour. Thus, 70 + 84 = 154 displays were assembled during the first two hours and 280 - 154 = 126 displays had not been assembled by the end of the second hour.