To solve this, you need to isolate/get the variable "n" by itself in the equation:
[tex]-\frac{6}{7} =\frac{n}{21}[/tex] Multiply 21 on both sides to get "n" by itself
[tex](21)(-\frac{6}{7} )=(21)\frac{n}{21}[/tex]
[tex]-\frac{126}{7} =n[/tex] Simplify the fraction
-18 = n
