EFG ~ LMN, if EF ~ LM, then whatever the number is for EF times whatever the others are multiplied by, you will get LM
for example:
FG (10) ~ MN (20)
if EF is (5), then LM is (10) (for you are multiplying by two.
Another example:
if FG is (100) ~ MN will be (200) (again for you are multiplying by two.
hope this helps