An equation is formed of two equal expressions. The total amount Mary had at the beginning was equal to $89.43.
What is an equation?
An equation is formed when two equal expressions are equated together with the help of an equal sign '='.
Given the money left with Mary is $11.43, therefore, the equation can be written as,
Amount Left = Total Amount with Mary - the cost of the electronics bought
Since the cost of the smartphone is $78. The Total amount can be written as,
$11.43 = Total Amount - $78
Total Amount = $78 + $11.43 = $89.43
Hence, the total amount Mary had at the beginning was equal to $89.43.
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