Jul 23, 2018 - 08:57 AM
In this case, "primero" is a determiner, specifically an ordinal number, so it goes before the noun. You will also see this when learning about courses of a meal. El primer plato. Or when getting directions. La segunda salida. Now, if you're getting hung up on "la vez pasada" as "last time," it is not "last" as in "first and last." You might instead literally translate it as "the time/occurrence that passed."
Let's use a noun that is a little easier to understand. Semana
La semana pasada - the week that passed - last week
La semana que viene - the week that comes - next week
La primera semana - the first week. i.e. La primera semana de julio - The first week of July
La ultima semana - the last week. i.e. La ultima semana de julio - The last week of July
Here are some useful links about adjective placement and a little more about types of determiners (in English).
Hope that helps!
Jul 23, 2018 - 11:39 AM