Short Answer: D
Look at them one at a time
Choice A
The result of multiplying 6 and m together (which is what you are supposed to do is 6m). This step is correct.
Choice B
There are no minus signs anywhere, either outside or inside the brackets, B is incorrect. Minus signs cannot be manufactured out of thin air. You need a reason.
Choice C
Same as B.
D is the correct answer. Both sides of a plus or minus sign have to be multiplied by what is outside the brackets. The plus sign cannot be destroyed unless you started out with something like
6 ( 4m + 3m) which = 24m + 18m = 42m But you could have combined like terms in the beginning.
6 * 7m = 42m
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