Can someone explain why this code outputs 4?

Question

var a = 6, b = 3, z = (++a - b) / (a % b);
document.write(z);

The way I see it is that a is that the variable a is pre-incremented and becomes 7 and is subtracted by b (which is 4), giving 3.
It is then divided by 6 mod 3 (which should be zero), and If you were to divide 3 by 0, it should output infinity.
Can someone explain what I'm doing wrong here?

Answer 1

first:
(++a - b) is gonna be 4

after that a become 7.

then:
(a % b) is going to be 1

finally:
4 / 1 gives us 4

Answer 2

(7-3)/(7%3) = 4/1 = 4

Answer 3

Thank you for the replies! Realized what I did wrong was that I forgot the fact that the variable retains it's added value if used with pre- and post-increments/decrements.