## The problem

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Is -7x+21 the same as 21-7x

## Answer provided by our tutors

Yes, -7x+21 is the same as 21-7x, that is:

-7x+21 = (-7x) + 21

Since the Commutative property of adding that states that 'a + b = b + a', if we put a = -7x and b = 21 we have:

a + b = (-7x) + 21

b + a = 21 + (-7x) = 21 - 7x

And that is exactly what is written above.