Do Pythagorean Theorem because a rectangle divided in diagonals form right triangles
A^2+b^2=C^2 
Plug in the correct numbers and solve 
A and B can be switched around but C is always the longest diagonal side which is called the hypotenuse not the Adjacent sides that form a right angle 
So with correct solving you should get 5.
        
             
        
        
        
Answer:
Y=21
Step-by-step explanation:
add 13 on both sides you get Y=21
 
        
             
        
        
        
Answer:
I can't see the picture
Step-by-step explanation: