LCM( 6, 18 ) = 18
The formula for finding LCM is
$$ \text{LCM} (a, b) = \frac{ a \cdot b }{ \text{GCD}(a,b)} $$In this example we have: a = 6, b = 18 and GCD(6, 18) = 6.
$$ \text{LCM} (6, 18) = \frac{ 6 \cdot 18 }{ \text{GCD}(6,18)} = \frac{ 108 }{ 6 } = 18 $$