Question

Can someone explain this to me because I'm confused.

http://prntscr.com/171l1o

Answer 1

The key to this problem is that the figures are similar.
The lengths of corresponding sides of similar figures are in proportion.

Answer 2

6x corresponds to 18, and 5x + 10 corresponds to 20
Write a proportion and solve it.

Answer 3

Uhh, would it be 6x/18 = 5x/10?

Answer 4

\[\large \frac{6x}{18}=\frac{5x+10}{20}\]

I think you had the right idea, I'm just not sure what happened on the right side.