Ellos comenzan las clases a las nueve.
Translated to they started classes at nine.
so comenzan is the right one
Salen = They go out (present time)
Salieron= They went out (past time)
Paco and Juan went out with their friends last Friday
Paco y Juan salieron con sus amigos el viernes pasado.
Seis y Diez is 6:10,
For the setence,
It is 6:10 at night.
You would say,
Son las Seis y Diez a la noche.
<h2>
¡A hacerlo!</h2>
1. They are fried potatoes.
2. It's a drink
3. It's a cookie
4. It's an ice cream
5. It's a pizza
6. They are some ice creams
7. They are fruits
8. It's a juice
<h2>
<em>De </em><em>nada.</em></h2>