Well, inspection can work here as 3/4 is obviously much larger than 1/6, but that obviousness is not always the case so we need common denominators. 12 will do here. Bring both fractions to common denominators with a form of one in a multiplicative fashion.
3*3/3*4 = 9/12
2*1/2*6 = 2/12
9/12 is obviously greater that 2/12 so 3/4 is greater than 1/6
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