I changed the code float b = to this because it did not compile:
float b = (x+15) / (y-6) * x/ (y*2) /3;
Once I did that then this line:
System.out.println("B= "+ b +" A = "+a);
gave this out put:
B= -0.33333334 A = 6.5
If you are looking for a certain output maybe you need to put () around what you want to calculate first.
What output are you expecting?