Question

how do you solve 3x-9=12

Answer 1

Given the equation:

$3x-9=12$

To solve for x, first we must pass the -9 to the other side of the equation. Since it has negative sign, we switch it when we pass it to the other side:

$\begin{gathered} 3x-9=12 \\ \Rightarrow3x=12+9 \end{gathered}$

Then, the 3 that multiplies the x must pass to the other side doing the opposite operation:

$\begin{gathered} 3x=12+9 \\ \Rightarrow3x=21 \\ \Rightarrow x=\frac{21}{3}=7 \\ x=7 \end{gathered}$

Therefore, x=7. We can check our answer by using this value on the original equation:

$\begin{gathered} x=7 \\ 3x-9=3\cdot7-9=21-9=12 \end{gathered}$