Solve classical stack-based problems, such as matching nested brackets or evaluating postfix expressions.
Implement solve_stack_problems(brackets, postfix_tokens). Return whether brackets is properly nested and the integer result of the valid postfix expression. Supported operators are +, -, *, and /, with division truncated toward zero. Inputs contain valid tokens and no division by zero.
def solve_stack_problems(brackets, postfix_tokens):