text: 0.07*X + 0.06 * (20,000-X) = 1280\n0.07*X + (1200 - 0.06*X)   = 1280\n(0.07 - 0.06)*X + 1200     = 1280\n0.01*X + 1200 - 1200       = 1280 - 1200\n0.01 * X                   =  80\n100 * 0.01 * X             = 80 * 100\nX = 8,000\n$8,000 was invested at 7%  and the remaining money 12,000 was invested at 6%