prob=Probability[Abs[x-y]≤5,{x,y}\[Distributed]ProductDistribution[{UniformDistribution[{0,30}],2}]];

Labeled[Show[RegionPlot[Abs[x-y]≤5,{x,0,30},{y,0,30},PlotStyle->Hue[.6,.5,.8]],ImageSize->350],Style[Row[{TraditionalForm[Pr[Abs[x-y]<5]],prob},"="],FontFamily->"Verdana"]]