## The problem

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Where does the the -7 =9 come from

## Answer provided by our tutors

If we add the same number to both sides of an equation, both sides will remain equal.

25x - 7 = 25x + 9 we add (-25x) to both sides of the equation

25x - 7 + (-25x) = 25x + 9 + (-25x)

25x - 7 - 25x = 25x + 9 - 25x

25x - 25x - 7 = 25x - 25x + 9

0 - 7 = 0 = 9

-7 = 9