Question 1133217
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1) 
Mr. Pickles owes $350 on his laptop. He has already paid $930 on it. What equation models determining the original cost of the laptop. 
This is my son's equation which was marked as incorrect :

350 + 930 = c ; c = 1280 
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Let c be the original cost (or price) of the laptop.
If Mr. P still OWES $350, and already paid  $930, then an equation using subtraction can be:   {{{c-930=350}}}.  
Also true can be this one, showing what what already paid:  {{{c-350=930}}}.