- Tämä harjoitus oli aika vaikea. - This exercise was quite difficult.
- Viime kerrasta on aika kauan aikaa. - It's been a while since the last time.
Another word for quite is melko, but I just realized that I never say it. I suppose it's a bit more formal than aika.
- Olen melko tyytyväinen suoritukseesi. - I'm quite satisfied with your performance.
- Käyn täällä melko usein. - I visit here rather often.
Notice that melko is very often mixed with melkein, which means almost.