let
the price of shirt = x
the price of the pair of pants = y
a. An equation to represent the total amount Barney spent can be represented below

b. An equation to describe the total amount spent by Robin in terms of number of shirt and pants can be written below

c. The equations formed can be solved below

d.
The co ordinates point where the two lines intersect is (10, 20) . It intersected point is the same with the x and y value when we solve the equation by using substitution method.
e. This means the price of each shirt is equals to $10 while the price of each pant is $20.