Here...see the attachment
 
        
        
        
First, distribute 2 to the (x+3) to get:
21 = 2x+6
subtract 6 from both sides to get:
15 = 2x
Finally, we divide both sides by 2 to simplify x to:
x = 7.5 (OR) x = 

(Just so you know, if you pick a brainliest answer, both you and the person who got the brainliest answer get some points.
 
        
        
        
Malia : y = 8.1x.....this tells me she makes 8.10 per hr worked
Bill : if he earned 144.90 for working 18 hrs.....144.90/18 = 8.05 per hr worked.
so Malia makes 5 cents more per hr worked.
Is that the answer ur looking for ?