Since you've already gotten a lot of suggestions for khan academy, which is good sure, let me give you another perspective.
KhanAcademy won't reply to you, won't adjust videos for your particular level or current difficulty.
A tutor will. So another suggestion to your question, especially since you've emphasized "quickly", I would suggest just hiring a tutor. Preferably in-person to be honest. You and the tutor, pencils and paper, will get you up to speed FAR quicker and more efficiently than watching youtubes.
Depending on your disposable income and time and setting, you might have a lot of very cheap college students willing to get you up to speed very quickly.
And when money's on the table, everyone takes things a bit more seriously, both you and the teacher. For your apparent needs, in my relatively low (not California for instance) cost of living area, you could find someone for 15-50 per hour. It also depends a lot. If you are enrolled in a college, then you likely have a tutoring center that can provide this for free. You could likely find folks who'd trade this for some beer or woodworking or I have no idea about you or your situation.
No matter what it's going to be *much* cheaper (US) than enrolling in a college and having a prof divide attention between you and the rest of the course members.
My suggestion would be a (in-person preferable) one-on-one tutor.