Answer:
Technically, 42×2=84
Explanation:
You could do this by adding 42+42=84
Multiplying 2 times the 2 and the 4, which gives you 84.
If you wanted the factoring then:
2 is a prime number
42 could be like 42
/ \
21 2
/ \
7 3
but I dont really know how factoring would help you multiply. I hope this helps