Evaluate $\left\lceil\sqrt{140}\right\rceil$.
I know that $\left\lceil x\right\rceil$ means the smallest integer that is greater than or equal to $x$. So, I want to find the smallest integer that is greater than or equal to $\sqrt{140}$. I can try to estimate $\sqrt{140}$ by squaring some integers. I know that $12^2 = 144$ and $11^2 = 121$, so $\sqrt{140}$ must be between $11$ and $12$. That means the smallest integer that is greater than or equal to $\sqrt{140}$ is $12$. Therefore, $\left\lceil\sqrt{140}\right\rceil = 12$. 