The mean age of 12 women in an office is 30 years old. The mean age of 6 men in an office is 25 years old.
What is the mean age (nearest year) of all the people in the office?

given the equation is 8+9z=-6, the first step would be to subtract the 8 from both sides:

8+9z-8=-6-8

since 8 minus 8 = 0, this would cancel out the 8. and since -6 minus 8 equals -14, the equation would look like this

9z = -14

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