Solution.
Let the number of pairs sold at $6 per pair be x
Let the number of pairs sold at $11 per pair be y
[tex]\begin{gathered} x+y=200-------(1) \\ 6x+11y=1600------(2) \end{gathered}[/tex][tex]\begin{gathered} Multiply\text{ equation \lparen1\rparen by 11} \\ 11x+11y=2200 \\ 6x+11y=1600 \end{gathered}[/tex][tex]\begin{gathered} Subtract\text{ both equations} \\ 11x-6x=600 \\ 5x=600 \\ x=\frac{600}{5} \\ x=120 \end{gathered}[/tex]Thus, the number of pairs of slippers sold at $6 each is 120
