Quantitative Reasoning

here is my issue im trying to get into college and i need to learn a lot of things in math although some how I passed everything but want to test out in math.... the only course i hit mid level at. I need to brush up on algebra and its talking alot about irrational numbers and all of that and square roots but i cant remember how to do them and there seems to be a ton of ways and most i dont understand and no way to ask anyone about them. i need exact answers and not approximations because it is for school and what im doing is dealing with alot of non perfect numbers like the square root of 122.... how do i do this in simple but detailed terms terms so that i can find the square roots of any number quickly and easily??? once i get it i wont forget it but getting it seems to be difficult on this subject for some reason. Thanks