What are factors and multiples of 12?
if you find the prime factors it makes the number easier to
multiple. first make prime factor trees for each of the numbers. i
did 18x15.
18 could have 3, 3 and 2 and 15 could have 3 and 5. then the sum
could be: 5x2=10x3=30x3=90x3=270
hope this helps. if you are not sure, look up prime factor trees
first.