Chapter 3.3, Problem 14P

Here’s how Mo solved the subtraction problem $635-813:$

     $\begin{array}{l}635\\ \frac{-813}{-222}\end{array}$

Mo did this by working form right to left, saying

     $\begin{array}{l}5-3=2\\ 3-1=2\\ 6-8=-2\end{array}$

1. Is Mo’s answer right?
2. Solve

     $\begin{array}{l}6(100)+3(10)+5(1)\\ \frac{-[8(100)+1(10)+3(1)]}{}\end{array}$

by working with expanded forms. Discuss how Mo’s work compares with

your work in expanded forms.