What is the value of the postfix expression 6 3 2 4 + – *?

The postfix expression is evaluated using a stack. Here are the steps:

1. Push 6 onto the stack.
2. Push 3 onto the stack.
3. Push 2 onto the stack.
4. Push 4 onto the stack.
5. Encounter '+', so pop 4 and 2 from the stack, add them to get 6, and push 6 onto the stack.
6. Encounter '–', so pop 6 (the result of 2+4) and 3 from the stack, subtract 3 from 6 to get 3, and push 3 onto the stack.
7. Encounter '*', so pop 3 and 6 from the stack, multiply them to get 18.

So, the value of the postfix expression 6 3 2 4 + – * is 18.