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. 
 
        
             
        
        
        
Subtract to find the amount of tax paid:
1890 - 1800 = 90
Divide the amount of tax by the price of the computer:
90 / 1800 = 0.05
Multiply the decimal by 100:
0.05 x 100 = 5%
The tax rate is 5%
 
        
             
        
        
        
For #7 - part a: greatest common factor (GCF) is 5.
Part b: cross out everything BUT 10 & 20. 
 
        
                    
             
        
        
        
Answer:(-8,-4)
Step-by-step explanation: