If I'm reading this correctly, it is 2*3*n*n = 6n^2
6n^2 = 54  Divide by 6
n^2 = 54/6
n^2 =  9      Take the square root of both sides.
sqrt(n^2) = sqrt(9)
n = +/- 3
n = + 3 or n = -3. Both will solve the equation above.
Edit
2 * 3 * n * n 
Let n = 3
2 * 3 * 3 * 3 = 6 * 9 = 54
The other value is n = - 2
2 * 3 * n * n
2 * 3 * (-3) * (-3)   A minus times a minus is a plus.
2 * 3 * 9 = 6 * 9 = 54
both + 3 and - 3 for n will give 54. 
 
        
             
        
        
        
Answer:
B
Step-by-step explanation:
 
        
             
        
        
        
Answer: 44
Step-by-step explanation:
1/5 of the slab are grey implies that 4/5 are yellow.
The ratio of grey to yellow is thus given as :
1/5 : 4/5
which is 1 : 4
Therefore , the ratio of grey to yellow is 1: 4
The total ratio = 1 + 4 = 5
To calculate the number of yellow , we use the formula
number of yellow =  X  total number of slabs , that is
 X  total number of slabs , that is
number of yellow =  X 55
 X 55
number of yellow slab = 44
 
        
             
        
        
        
A = 1/2 bh = 1/2 (3)(4) = 12/2 = 6
answer is B. 6 square units
        
             
        
        
        
7 is 1/4 of 28, so 7 is 25% of 28.
The drop from 28 to 7 is a drop of 21.
21 is 3 times 7, so 21 is 3 times 25%.
Answer: It is a 75% decrease.