Here's the best I can come up with:
Manipulate[
Plot[((a/(1 - b)) + (b/(1 - b))*X), {X, 0, 100},
PlotRange -> {{0, 100}, {0, 300}}, AxesOrigin -> {0, 0},
LabelStyle -> Directive[12], AxesLabel -> {"X-axis", "Y-axis"},
Ticks -> {{{X/2,
X}}, {{((a/(1 - b)) + (b/(1 - b))*
X/2), ((a/(1 - b)) + (b/(1 - b))*X)}}},
Epilog -> {{Dashed,
Line[{{X/2,
0}, {X/2, ((a/(1 - b)) + (b/(1 - b))*X/2)}}]}, {Dashed,
Line[{{X/
2, ((a/(1 - b)) + (b/(1 - b))*
X/2)}, {0, ((a/(1 - b)) + (b/(1 - b))*X/2)}}]}, {Line[{{{0,
185}, {9, 182}, {18, 177}, {27, 170}, {33, 163}, {40,
152.5}, {45, 143}, {50.5, 129}, {56, 112}, {60, 96}, {62.5,
83}, {65, 68}, {67, 50}, {69, 20}, {70, 0}}}]}}], {{a, 30},
0, 50}, {{b, .6}, .0000001, 1}, {{X, 90}, 0, 100}]
I plotted the production possibility curve with the
Line[{{0, 185}, {9, 182}, {18, 177}, {27, 170}, {33, 163}, {40, 152.5}, {45, 143}, {50.5, 129}, {56, 112}, {60, 96}, {62.5, 83}, {65, 68}, {67, 50}, {69, 20}, {70, 0}}]
Any ideas how to make this simpler? Any ideas how make the curve smoother?