Question

Two common multiples of 3&7 less then 50

Answer 1

3 = 1 X 3
7 = 1 X. 7

Therefore LCM = 1 X 3 X 7
LCM = 21

If I times 21 by 2 then I should get another multiple

So 21 X 2 = 42

Hence the two multiples of 7 and 3 below 50 are 21 and 42.

Answer 2

21 and 42 are the common multiples ...