Step-by-step explanation:
This is a simple system of equations problem, with our equation being:
[tex]\frac{4}{7}x+9=x[/tex]
We know this as her dogs (x) is equal to 4/7 of her dogs (x) plus 9. Now all we must do is solve for x:
[tex]\frac{4}{7}x+9=x\\\\\frac{4}{7}x=x-9\\\\\frac{4}{7}x=\frac{7}{7}x-9\\\\\frac{-3}{7}x=-9\\\\x=21[/tex]
