3-6n = 21

the answer is n=4 but i want to know how to get there.

Our current equation is:
3 -6n = 21

To solve for n, we need to get -6n by itself on one side, and then simplify.

Always remember;
What you do to one side of an equation, you must do to the other.

Subtract 3 from both sides.

3 - 3 = 0
21 - 3 = 18.

Your equation now is:
-6n = 18.

N is being multiplied by -6, so we need to perform the opposite order of equations.

Divide both sides by -6.

-6n / -6 = n
18 / -6 = -3

n = 3

I hope this helps!