Chapter 5.1, Problem 13MC

A fourth-grade student devised the following algorithm for subtracting $84-27$:

$4$ minus $7$ equals negative $3$.

$\begin{array}{l}84\\ \underset{\_}{-27}\\ 3\end{array}$

$80$ minus $20$ equals $60$.

$\begin{array}{l}84\\ \underset{\_}{-27}\\ 3\\ 60\end{array}$

$60$ plus negative $3$ equals $57$.

$\begin{array}{l}84\\ \underset{\_}{-27}\\ 3\\ \underset{\_}{+60}\\ 57\end{array}$

Thus, the answer is $57$. How should you respond as a teacher? Will this technique always work?