Spanish says it makes two weeks to mean two weeks ago.
hace dos semanas = two weeks ago
Lo vi hace dos semanas · Le respondí hace siete semanas · Se lo respondí hace un mes
The full set is now complete.
-aste / -iste = you (informal) · -aron / -ieron = they
¿Comiste? · ¿No lo comiste? · ¿Saliste? · ¿Saliste anoche? · ¿Dónde viviste? · ¿Me esperaste? · ¿Por qué no me esperaste? · ¿Cuándo llegaste? · Esperaron · Lo prepararon · Salieron · Los vendieron
A neat symmetry worth seeing. In the present, -er and -ir verbs are dominated by e, with i appearing just once, in vivimos. In the point past it is exactly inverted.
That single e in -ieron is there to remind you this is the -er group too, not just -ir.
And across the two groups: the -er/-ir forms are the -ar forms with that important i pushed in.
hablé → comí · habló → comió · hablamos → comimos · hablaste → comiste · hablaron → comieron
Rather than I responded to her mail, Spanish says I responded her the mail, which sounds wrong in English but is perfectly natural Spanish.
Se lo respondí (I responded it to her)
There the se is really le, to her, and the lo is the mail. Spanish does not use possessive words nearly as much as English does.
Both of these are fine, and the choice reflects only what the speaker had in mind.
Some cases lean strongly one way. ¿Cuándo llegaste? needs the point, because you would not ask when were you arriving.
Discriminé · Discriminó · Discriminamos