Question

Three times the sum of a number and nine is 12. Find the number.

Short answer

The number is $-5$.

Step-by-step solution

Step 1. Given information

Three times the sum of a number and nine is 12.

Step 2. Forming linear equation

Let the required number be $x.$

Then,$3\left(number+9\right)=12$

Step 3. Finding the number

$$\begin{gathered} 3(x+9)=12 \\ 3x+27=12 \\ 3x=12-27 \\ 3x=-15 \\ x=-5 \end{gathered}$$