Answer:
Quinzel sold 17 pairs of shoes last month.
Step-by-step explanation:
Let be "Q" the number of pairs of shoes Quinzel sold last month and "J" the number of pairs of shoes Joseph sold last month.
Set up a system of equations:
[tex]\left \{ {{Q=J-18} \atop {Q+J=52} \right.[/tex]
Solve for "J" from the first equation:
[tex]J=Q+18[/tex]
Applying the Substitution Method, you get:
[tex]Q+J=52\\\\Q+(Q+18)=52\\\\2Q=52-18\\\\Q=\frac{34}{2} \\\\Q=17[/tex]