Question

The expression -3m - [2m + (5 - m)] + 7 was simplified as 2 - 4m.

Answer 1

-3m - [2m + (5 - m)] + 7
= -3m - 2m - 5 + m + 7
= -4m + 2 
or
= 2 - 4m

Answer 2

Question:  The expression -3m - [2m + (5 - m)] +7 was simplified as 2 - 4m.  Without simplifying, explain how you can show that it has been simplified correctly.

Answer may include:

If the expression has been simplified correctly, then the expressions will be equivalent.

The expressions will have the same value when numbers are substituted in for the variable m.

Choose a value for m and substitute in to both expressions.

Simplify each expression using the order of operations and show they are the same value.