Assume the old of Jack is X and the old of Lacy is Y 
so ... 
do the mathematical model ...
.
X=2Y
(X+7)+(Y+7)= 35 
-
THEN 
Solve the equation 
y= 7 
x = 14 
        
             
        
        
        
Answer:
16,244.55
Step-by-step explanation:
Original cost of piano = 19,100
19% off on 19,100 = 0.19*19100 = 3,629
Selling cost = 19100 - 3629 = 15471
Sales tax = 5% =0.05
Amount of sales tax = 0.05*15471 = 773.55
Total selling cost of piano = Selling cost + Amount of sales tax = 15471 + 773.55 = 16,244.55
 
        
                    
             
        
        
        
Answer: B 
Step-by-step explanation: Look at where the lines intersect