The largest triangle inscribed in a square is half of the square. Thus, its area is equal to 12*12/2 = 72. Side equal to 12 comes from the fact that the diameter of the inscribed circle is 12.

The area of the inscribed circle is 6*6*pi = 36*pi.

Now, we have to compare 72 and 36*pi. We can rewrite 72 as 36*2 and compare 2 and pi. Since pi = 3.14 it is larger than 2 and quantity B is greater