To solve for x you can first divide by 12 into both sides of the equation, like this
[tex]\begin{gathered} \frac{12\mleft(x-2.3\mright)}{12}=\frac{15.6}{12} \\ x-2.3=1.3 \end{gathered}[/tex]Now, you can add 2.3 from both sides of the equation
[tex]\begin{gathered} x-2.3+2.3=1.3+2.3 \\ x=3.6 \end{gathered}[/tex]Therefore, the value of x that satisfies the equation is
[tex]x=3.6[/tex]Finally, to check that this value satisfies the given equation, just plug x = 3.6 into the equation and see that a true proposition is reached. So, you have
[tex]\begin{gathered} 12\mleft(x-2.3\mright)=15.6 \\ \text{ Replace x = 3.6} \\ 12(3.6-2.3)=15.6 \\ 12(1.3)=15.6 \\ 15.6=15.6 \\ \text{ True proposition} \end{gathered}[/tex]