LCM( 12, 18 ) = 36
The formula for finding LCM is
$$ \text{LCM} (a, b) = \frac{ a \cdot b }{ \text{GCD}(a,b)} $$In this example we have: a = 12, b = 18 and GCD(12, 18) = 6.
$$ \text{LCM} (12, 18) = \frac{ 12 \cdot 18 }{ \text{GCD}(12,18)} = \frac{ 216 }{ 6 } = 36 $$