A letter written by Albert Einstein in which he writes out his famous E = mc 2 equation has sold at auction for more than $1.2 million, about three times more than it was expected to get, Boston-based ...

'I think of a number, add four, and the answer is seven.' Written algebraically, this statement is \(x + 4 = 7\), where \(x\) represents the number you thought of. \(x + 4 = 7\) is an example of an ...