With[{opt = {ImagePadding -> 30, ImageSize -> 500, BaseStyle -> Thick}},
 Overlay[{
   ListLinePlot[Reverse@area[[ ;; , 2]], Frame -> {{1, 0}, {0, 0}}, opt, PlotStyle -> Red,
                                         FrameStyle -> Red,  DataRange -> {0, 21}],
   ListLinePlot[Reverse@distance[[ ;; , 2]], opt, Frame -> {{0, 1}, {0, 0}}, 
                                             FrameStyle -> Blue, PlotStyle -> Blue,
                                             DataRange -> {0, 21}, 
                                             FrameTicks -> {{None, All}, {None, None}}], 
   Plot[, {x, 0, 21}, opt, Axes -> False, Frame -> {{0, 0}, {1, 1}}, 
        FrameTicks -> {{None, All},
                      {{#, If[OddQ[#], 21 - #, ""]} & /@ Range[0, 21, 1/2], None}}
       ]      
   }]]