B. 7
Explanation
Step 1
Let the rosita's mom age=45
a represents the age of rosita
and
the rosita's mom age=42
she is six times as old as Rosita,so
[tex]6a=42[/tex]Step 2
solve the equation
[tex]\begin{gathered} 6a=42 \\ \text{divide both sides by 6} \\ \frac{6a}{6}=\frac{42}{6} \\ a=7 \end{gathered}[/tex]it means the age of rosita is 7
so, the answer is
B.7
I hope this helps you
