what is the soulution for x +9 =21

To solve the equation \( x + 9 = 21 \), follow these steps:

1. Subtract 9 from both sides of the equation:

\[
x + 9 - 9 = 21 - 9
\]

2. Simplify:

\[
x = 12
\]

So the solution is \( x = 12 \).