I will give you the points so that you can draw the graph
x y
(number of chairs assempled in 20 days) (number of tables assembled in 20 days)
0 5
4 4
8 3
12 2
16 1
20 0
Then the graph of the function y = 5 - x/4 will pass for all those points. It will intersect the y-axis at 5 and the x-axis at 20. Note that this mean tha if she makes 0 chairs she will make 5 tables, and if she makes 20 chairs she will make 0 chairs.
The function y = 5 - 4/x is continuos, but the real function of assembly is discrete, because she cannot assemble a fraction of chairs or a fraction of tables.