The trick you need to know is the theorem that says that if the digits in a number add up to a multiple of 9, then the number itself is divisible by 9.
So we go 4+3+2 = 9.
So as this sum of 9 is divisible by 9, it means 432 is also divisible by 9.
If you want to work out the actual answer of 432 divided by 9, you can estimate it by doing 450 ÷ 9 = 50. Then see that 432 is 18 less than 450. And 18 = 2x9. So the answer to the division is 50-2 = 48.
