God why can't i understand thus stuff

Hey there,
For this question, you need to find the lowest common multiple which in this case is 60. 
How i got it?
5= 1 x 5
12= 2 square x 3
Since one is common, take 5 x 2 square x 3 which is equal to 60

Hope you get it :))

You can ask me any doubts if you have :))

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