Thus is a linear equation, so you want to isolate m so you can compare the variable m to a constant.
You begin by getting rid of -9 by adding 9 (its opposite) since a negative plus a positive can me zero. Then you add 9 to (-13) which is the same as 13-9 but with a negative value, so you get -4.
The answer is -4
You begin by getting rid of -9 by adding 9 (its opposite) since a negative plus a positive can me zero. Then you add 9 to (-13) which is the same as 13-9 but with a negative value, so you get -4.
The answer is -4