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Anna and David left an 18% tip after having dinner at a restaurant. The amount of the tip was $9. Anna’s dinner cost $28. Which equation can you use to find x, the cost of David’s dinner?

 Jan 21, 2021
 #1
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Call the cost of David's dinner D.  

 

9  =  0.18 • (D + 28)       The tip equals 18% of the total of David's and Anna's dinners.

 

9  =  0.18D + (0.18 • 28)  

 

0.18D  =  9 – 5.04           I switched sides because I like the unknown on the left.  It's a personal preference. 

 

0.18D  =  3.96  

 

          3.96  

D  =  ———  =  22           David's dinner cost $22.00  

          0.18  

.

 Jan 21, 2021
 #2
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.18x =  $ 9

x = 9/.18 = total dinners' cost = $ 50      David's dinner:  $ 50 - 28 = $22

 Jan 21, 2021

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