Question 882355
Answering can only be done using symbols because you do not show your figure and you give no variable names nor values.


The rectangle part has dimensions x and y, and the semicircle's diameter x, will match the x dimension of the rectangle.  The fence material length needed will be 1*x+2*y, for the three straight sides of the rectangle, and then (1/2)(2*pi*x) for the half-circle part.


The sum of all those is {{{highlight_green(x+2y+pi*x)}}};
That's it, until you know some values or know how they are further related.