1) In this problem, we need to bear in mind that we can find the original selling price by making use of an equation:
[tex]\begin{gathered} M=\$10.45 \\ N=\$6.45 \\ M=S-N \\ 10.45=S-6.45 \\ 10.45-S=S-S-6.45 \\ 10.45-S=-6.45 \\ -S=-6.45-10.45 \\ -S=-16.9 \\ S=16.9 \end{gathered}[/tex]Thus, the original selling price is:
[tex]\$16.9[/tex]