What is the unit value the 3 in 432 ?

It represent the tens of the number, therefore, it's unit value is 30

Explanation:
The place value chart is added in the attached image.

Checking this chart, we would find that:
first digit from the right is the units of the number
second digit from the right is the tens of the number
third digit from the right is the hundreds of the number

Comparing this with the nuber given, we would find that the 3 is in the tens position. Therefore, it unit value is 30.

Another way to answer this is by breaking the number given as follows:
432 = 400 + 30 + 2
We can note that the unit value of the 3 is 30

Hope this helps :)