Question 239176
18%=.18 in decimal.
Let x be the cost of the meal & .18x be the amount of the tip. 
total cost=meal+tip 
40.71=x+.18x [1x+.18x=1.18x]
1.18x=40.71
x=40.71/1.18
x=$34.50 was the price of the meal before the tip.
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IF YOUR COMMENTS ARE VALID THEN I MUST OFFER A OPINION:
Either the school rules are ridiculous.
Your teacher doesn't know how to solve these problems.
Or you have no taxt books with proper examples.
WHATEVER THE CASE, THE SCHOOL SYSTEM IS AT FAULT FOR NOT TEACHING, WHICH IS WHAT I ASSUME THEY ARE BEING PAID TO DO. 
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