Question

ΔEFG ~ ΔLMN. Find LM.

Answer 1

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 

Answer 2

The solution is 2.5. The problem can be solved using the proportion:  

2

4

=

x

5