Write a PL/SQL block to show the operator precedence and parentheses in several more complex expressions

DECLARE
  salary      NUMBER := 40000;
  commission  NUMBER := 0.15;
BEGIN
  -- Division has higher precedence than addition:
  
  DBMS_OUTPUT.PUT_LINE('8 + 20 / 4 = ' || (8 + 20 / 4));
  DBMS_OUTPUT.PUT_LINE('20 / 4 + 8 = ' || (20 / 4 + 8));
  
 -- Parentheses override default operator precedence:
 
  DBMS_OUTPUT.PUT_LINE('7 + 9 / 3 = ' || (7 + 9 / 3));
  DBMS_OUTPUT.PUT_LINE('(7 + 9) / 3 = ' || ((7 + 9) / 3));
 
  -- Most deeply nested operation is evaluated first:
 
  DBMS_OUTPUT.PUT_LINE('30 + (30 / 6 + (15 - 8)) = '
                      || (30 + (30 / 6 + (15 - 8))));
 
  -- Parentheses, even when unnecessary, improve readability:
 
  DBMS_OUTPUT.PUT_LINE('(salary * 0.08) + (commission * 0.12) = '
    || ((salary * 0.08) + (commission * 0.12))
  );
 
  DBMS_OUTPUT.PUT_LINE('salary * 0.08 + commission * 0.12 = '
    || (salary * 0.08 + commission * 0.12)
  );
END;
/