This Problem Set is part of the the Lesson 1, Unit 2, Grade 5. Look at your Problem Set. Did anyone answer #3g without evaluating the expressions? How were you able to do that? When evaluating the expression in #5, a student got 18. Can you identify the error in thinking? Look at #7. How did you know what to evaluate first with so many sets of grouping symbols? Why do we use parentheses in mathematical expressions? When is it important to use parentheses? When are parentheses not necessary?