The chord 3cm away is 12cm and chord 6cm away is 6cm. 
The two perpendicular chords will create a rectangle with the center. each side will be half of the parallel sides length. 
        
                    
             
        
        
        
9^2 = 2x^2
81 = 2x^2
40.5 = x^2
6.36 = x
I think the side length of the square would be around 6.36 cm.
**i don’t know if this is right
        
             
        
        
        
Look up online "equation calculator" and it should be the first one to appear, "Symbolab" supper easy way to help you with problems!
        
             
        
        
        
Answer:
A) 12.5%
B) 50%
C) 50%
Step-by-step explanation:
For A, 7 is one of the 8 possibilities (1/8). 1/8 of 100 is 12.5, so your chance of spinning a 7 is 12.5%
For B, even numbers are 4/8 or 1/2 of your options. 1/2 of 100 is 50, so your chance of spinning an even number is 50%
For C, there are 4 out of 8 numbers that are prime (2,3,5, & 7).
4/8 or 1/2 of 100 is 50, so your chance of spinning a prime number is 50%
hope this helps