Chapter 3.2, Problem 8P

To calculate $159-73,$ a student writes the following equations:

   $160-70=90-3=87-1=86$

Although the student has a good idea for solving the problem, his equations are not correct. In words, describe the student’s solution strategy and discuss why the strategy makes sense; then write a correct sequence of equations that correspond to this solution strategy. Write your equations in the following form:

    $159-73=\text{some expression}$

      $=\text{some expression}$

      $=:$

      $=86$