I hope this helps you 
4,8 (x+4)=2,16
48 (x+4)=21,6
x+4=21,6/48
x+4= 0,45
x=0,45-4
x= -3,55
        
                    
             
        
        
        
There were 200 students that attend the dance. 
        
             
        
        
        
There are 18 girls in the class and 6 boys.
        
             
        
        
        
If we have a circle with a radius of 3 we need to find the diameter of the circle.  Remember radius is half of the diameter.  So, the diameter is 6 units.
Use the circumference formula: C=3.14D
C=3.14(6)
C=18.84 units