daten1 = {{2, 0.3}, {4, 2.0}, {7, 8.1}, {9, 46.2},
          {11, 107.1}, {14, 105.1}, {16, 96.0},
          {18, 82.8}, {21, 81.7}, {23,79.1}, {25,88.2}}; 
daten2 = {{2, 0.2}, {4, 0.8}, {7, 9.9}, {9, 23.3},
          {11, 59.4}, {14, 87.1}, {16, 124.7}, 
          {18, 115.6}, {21, 94.7},{23, 91.4}, {25,100.5}};
bild1 = ListPlot[daten1, PlotJoined -> True,ImageSize->{400,300}];
bild2 = ListPlot[daten2, PlotJoined -> True,ImageSize->{400,300},
                 PlotStyle->Dashing[{0.01}]];
bild = Show[bild1,bild2,ImageSize->{400,300}];