The cost of the watch originally cost $1,640.31
        
             
        
        
        
Answer:
x= -5 
Step-by-step explanation:
3(5x+10)+10=6x-(x+10)
15x+30+10=6x-x-10
15x+40=5x-10
15x-5x=-10-40
10x=-50
x=-5
 
        
                    
             
        
        
        
The sum of two consecutive even integers is a+(a+2) and divided by four is
(a+(a+2))/4 = 189.5
(2a+2)/4 = 189.5
2a+2 = 189.5 * 4
2a+2 = 758
2a = 758 - 2
2a = 756
a = 756/2 = 378
first number is a = 378
second number is a+2 = 378+2 = 380