Reducing a fraction to lowest terms

Statement

Reduce the fraction to lowest terms: $\frac{204}{357}.$

Solution

Factor the numerator and the denominator: $204 = 2^2\cdot 3\cdot 17, \qquad 357 = 3\cdot 7\cdot 17.$ The common factor is $3\cdot 17 = 51$, which is the GCD. Dividing both by $51$: $\frac{204}{357} = \frac{204:51}{357:51} = \boxed{\dfrac{4}{7}}.$