1. Three years ago, Rosa's mother was exactly five times as old as Rosa was then. Rosa's mother was then exactly as old as Rosa's grandmother was at the moment Rosa's mother was born. $\mathrm{Now}$ Rosa's grandmother is exactly seven times as old as Rosa herself.

How old is Rosa's mother now?
B1. 33 years Given that Rosa's mother was five times as old as Rosa was three years ago. From the data, we also deduce that Rosa's grandmother was twice as old as Rosa's mother at that time. We conclude that Rosa's grandmother was ten times as old as Rosa was then.

Let's call Rosa's current age $x$. Her grandmother was therefore $10(x-3)$ years old three years ago. It is given that she is now 7 times as old as Rosa. Three years ago, she was thus $7 x-3$ years old. Therefore, it must hold that $10(x-3)=7 x-3$. Simplifying gives $3 x=27$ and thus $x=9$. Three years ago, Rosa was therefore $9-3=6$ years old. Rosa's mother was then $5 \times 6=30$ years old and is now thus 33 years old.