Question 1205211
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an order of 2 bags French Fries and 1 burger costs $5.80.<s>An order of 1 burger costs 5:80.</s>
An order of 1 bag of French fries and 2 burgers costs $6.20 .What is the cost of 
an order of 3 bags of French fries and 3 burgers in dollars?
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f price of french fries
b price of burger


{{{system(2f+b=5.8,f+2b=6.2)}}}


If the members are added then  {{{3f+3b=5.8+6.2}}}, and this left member is the expression described in the question.


{{{3b+3f=highlight(12)}}} dollars