8(9s+15)=6(4s-4)

8(9s+15)=6(4s-4)

$$\small{\text{$
\begin{array}{rcl}
8(9s+15) &=& 6(4s-4) \\
8\cdot 9s+8\cdot 15 &=& 6\cdot 4s - 6\cdot 4 \\
72s + 120 &=& 24s - 24 \quad | \quad - 24s\\
72s-24s + 120 &=& -24 \\
48s +120 &=& - 24 \\
48s +120 &=& - 24 \quad | \quad - 120\\
48s &=& - 24- 120\\
48s &=& -144\\
48s &=& -144 \quad | \quad :48\\\\
s & =& -\dfrac{144}{48} \\\\
\mathbf{s} & \mathbf{=} &\mathbf{ - 3 }
\end{array}
$}}\\\\\\\\
\small{\text{$\mathbf{check:}
\begin{array}{rcl}
8\cdot [9(-3)+15] &=& 6\cdot [4(-3)-4]\\
8\cdot (-27+15) &=& 6\cdot (-12-4)\\
8\cdot (-12) &=& 6\cdot (-16) \\
-96 &=& -96 \qquad \mathrm{okay}
\end{array}
$}}$$