I feel like I know the answer but I also feel like I am missing some. What are the correct answers to this question?

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

Sum is 17 and their difference is 3

The figures below are made out of circles, semicircles, quarter circles, and a square. find the area and the perimeter of each figure and give your answers as a completely simplified exact value in terms of π (no approximations).