Stacks - General Questions

Evaluate the postfix expression: 8 6 * 7 2 * -

Evaluate the postfix expression: 2 9 * 9 2 * -

Starting with an empty stack, these operations are performed: push(9), push(8), pop(), push(4), pop(), push(4), push(1). What is at the top of the stack now?

Evaluate the postfix expression: 5 8 + 3 *

Evaluate the postfix expression: 5 3 - 9 +