The question is asking you to solve for your variable N. To do so, you must use difference operation(s) and their respective principle of equality to isolate the variable.
To get n by itself on one side of the variable, the term -7n by -7. What you do to one side of the equal sign, you must also do to the other due to the division principle of equality. Thus, you also divide 21 by -7.
Once you simplify, you are left with -3 = n or n = -3, which is your answer.
First you divide 126 by 7 (number of women) and you get 18 then you times that by 5 (total number of men) and you get 90 finally you add 90 (men) and 126 (women) to get 216 employees in total.
