-6n+21=12n-15
Subtract 12n from -6n so that the variable n is only on one side.
-18n+21= -15
Subtract 21 from 15
-18n= -36
Divide both sides by -18 so that the only thing remaining on the left side is the variable n.
Final Answer: 2 *Note: When you divide a negative number by another negative number, it creates a positive number.