Explanation:
First we have to find multiples of 18 and multiples of 45:
[tex]\begin{gathered} 18\colon18,36,54,72,90,108\ldots \\ 45\colon45,90,135\ldots \end{gathered}[/tex]From these multiples we have to identify which one is common for both numbers (it appears in the multiples of 18 AND 45) and is the least. In this case 90 is the least common multiple.
Answer:
LCM: 90