a="13";
b="10";
c="210.2";
d="36.5";
d=ToString@(N[ToExpression@c/ToExpression@d]);
g1=Plot[PDF[FRatioDistribution[ToExpression@a-1,ToExpression@b-1],x],{x,-1,ToExpression@d+3},Filling->Axis,PlotLabel->Column[{Style["F-Distribution",Bold],Grid[{{"(Subscript[F, STAT]) = \!\(\*FractionBox[\(\(\\ \)\*SuperscriptBox[SubscriptBox[\(S\), \(NS\)], \(2\)]\(\\ \)\), SuperscriptBox[SubscriptBox[\(S\), \(N\)], \(2\)]]\) = "<>ToString[d]}},Frame->All],""},Alignment->Center], PlotRange->Full,AxesOrigin->{0,0},Ticks->{{ToExpression@d},None}];
g2=Plot[PDF[FRatioDistribution[ToExpression@a-1,ToExpression@b-1],x],{x,ToExpression@d,7},Filling->Axis, PlotRange->Full,AxesOrigin->{0,0},PlotStyle->Directive[Black,Dashed], FillingStyle->{Orange}];


h1=NSolve[CDF[FRatioDistribution[ToExpression@a-1,ToExpression@b-1],ToExpression@d]==1- (ToExpression@x),{x}, Reals];
h=x/.h1[[1]];
Show[g1,g2,Graphics[{
Dashed,
Black,Line[{{ToExpression@d,0},{ToExpression@d,1}}],
Text[Style["p-value = "<>ToString@h,Small,Bold],{ToExpression@d+2,0.3}],
Arrow[BezierCurve[{{ToExpression@d+2,0.25},{ToExpression@d+2,0.05},{ToExpression@d+1,0.01}}]]
}],ImageSize->400]

a="12";
b="14";
d="1.8";(*ts*)
c="1.76"; (*ta*)
n=ToString@(ToExpression@a+ToExpression@b-2);
g1=Plot[PDF[StudentTDistribution[ToExpression@n],x],{x,-7,7},Filling->Axis,PlotLabel->Style["t Distribution\nα = 0.05\n(Subscript[t, α]) = "<>ToString[ToExpression@c],Bold], PlotRange->Full,AxesOrigin->{0,0},Axes->{True,False},Ticks->{{ToExpression@c},None}];
g3=Plot[PDF[StudentTDistribution[ToExpression@n],x],{x,ToExpression@c,7},Filling->Axis, PlotRange->Full,AxesOrigin->{0,0},Axes->{True,False},PlotStyle->Green, FillingStyle->{Green}];
Show[g1,g3,Graphics[{
PointSize[0.01],Point[{ToExpression@d,0},VertexColors->Blue],
Dashed,Red,Arrowheads[{-.03,.03}],Arrow[{{-7,0.2},{ToExpression@c,0.2}}],Text[Style["Do not reject (Subscript[H, 0])",Medium,Bold],{-3,0.22}],
Green,Arrow[{{ToExpression@c,0.2},{7,0.2}}],Text[Style["Reject (Subscript[H, 0])",Medium,Bold],{5,0.22}],
Black,Line[{{ToExpression@c,0},{ToExpression@c,0.3}}],
Text[Style["(Subscript[t, STAT])",Medium,Blue,Bold],{ToExpression@ts,0.03}]
}],ImageSize->400]