let's do it cheaply, hmmm hmmm let's take a peek at all the denominators, hmm 4, 10, 5, 2 and 20, so we can say the LCD of all those guys is "20".
Now, let's multiply all by the LCD of 20, what that does, is in essence gives us the fraction of a twentieth, making all the fractions at the same "20" level, or namely if we put all fractions with the same denominator of 20, it gives us the numerator, and the highest, well, that's our guy.
