That is the power of precedence.
The multiplication will take the power. thats int y =a-b++ * --b;
you need to put them in a correct arragement depending on what you want to achieve such as.
1. int y = (a - b++)*--b;
2. int y = a-(b++ * --b);
Any selection above will at least provide you with a constant answer because the compiler will explicitly understand your intention.