Answer: 21 = c
Step-by-step explanation: To solve this equation for n, we need to get n by itself on the right side of the equation. Since 9 is being subtracted from n, in order to get n by itself, we need to add 9 to the right side of the equation but if we add 8 to the right side of the equation, we also add 8 to the left side of the equation.
On the right side of the equation, the -9 and +9 cancel each other out and we are simply left with n. On the left side of the equation, 12 + 9 is 21 so we have 21 = c which is the solution to our equation.
To check our solution, we can plug 21 back in for n in the original equation. So we have 12 = 21 - 9 or 12 = 12.
Since 12 = 12 is a true statement, we know that our solution is correct.
If you're having trouble adding and subtracting positive and negative integers, you may want to review this idea before continuing with equations.
