Ineed to find the area of the shaded part. i have the height of the triangle. but i dont know how to get the base of the triangle so i can figure out the area of the triangle.

Nick has box brads. he uses 4 brads for the first project. nick let’s b represent the original number of brads and finds that for the second project, the number of brads he uses is 8 more than half the difference of b and 4. write an expression to represent the number of brads he uses for the second project.