An algebraic expression is an expression that includes constants, variables, and the algebraic operations (add, subtract, multiply, divide.
        
             
        
        
        
both angles would equal the same so you have:
6x-57 = 2x+15
add 57 to each side:
6x = 2x+72
subtract 2x from each side:
4x = 72
 divide:
x = 72/4 = 18
now replace x with 18:
6(18) - 57 = 51
2(18) +15 = 51
51 +51 = 102
Angle QNR = 102 degrees
 
        
             
        
        
        
To find the total cost, you need to add these numbers together 

you get 7.37 as your answer, but you need to round this to the nearest whole number. 
rounding 7.37 will make it 7. 
the total cost is about $7