Let x be the number of box cards
Expenditures: $22 plus $4 times x
[tex]E=22+4x[/tex]Sales: $15 times x
[tex]S=15x[/tex]At some point, she will sell enough cards so that her sales of her cover her expenditures of her: Equal E and S
[tex]E=S[/tex]Substitute the values of E and S:
[tex]22+4x=15x[/tex]Solve x:
[tex]\begin{gathered} 22+4x-4x=15x-4x \\ 22=11x \\ \frac{22}{11}=\frac{11}{11}x \\ 2=x \\ \\ \\ x=2 \end{gathered}[/tex]Use the value of x to find the sales and expenditures:
[tex]\begin{gathered} S=15x \\ S=15(2) \\ S=30 \\ \\ E=22+4x \\ E=22+4(2) \\ E=22+8 \\ E=30 \end{gathered}[/tex]