A MATHS RIDDLE

Here's a classic Maths riddle in both Spanish and English version:

Yendo yo hacia Villavieja,
me encontré con siete viejas.
Cada una llevaba siete sacos;
cada saco, siete ovejas.
¿Cuántas viejas, sacos y ovejas
iban para Villavieja?

As I was going to Saint Ives,
I came across seven wives.
Each wife had seven sacks.
In each sack there were seven cats.
How many cats, sacks, and wives
were going towards Saint Ives?