Answer:
Step-by-step explanation:
I have attached a written explanation to help :).
Let's say each side of the square =
If we put 7 squares in a row to make the rectangle,
length of the rectangle =
Area of a rectangle = length multiplied by width
Area of rectangle =
multiplied by
=
We are also told that the total area = 567
So 
Now solve for
.
Divide both sides by 7.


Then square root both sides to find 
= 9
Finally, the question asks to find the length of the collage which we said was
and we know 
Length of collage =
multiplied by
= ?