-5/2(w-1)=15

(-5/2)(w-1)=15      multiply both sides by -2/5

w - 1  = 15(-2.5)    simplify

w - 1 = -6      add 1 to both sides

w = -5

W=5

$$\underset{\,\,\,\,{\textcolor[rgb]{0.66,0.66,0.66}{\rightarrow {\mathtt{w}}}}}{{solve}}{\left(\begin{array}{l}{\mathtt{\,-\,}}\left({\frac{{\mathtt{5}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}\left({\mathtt{\,-\,}}{\mathtt{5}}{\mathtt{\,-\,}}{\mathtt{1}}\right)\right)={\mathtt{15}}\\
{\mathtt{\,-\,}}\left({\frac{{\mathtt{5}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}-{\mathtt{6}}\right)={\mathtt{15}}\\
\left({\frac{{\mathtt{5}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}{\mathtt{6}}\right)={\mathtt{0}}\\
{\mathtt{15}}={\mathtt{0}}\\
{\mathtt{W}}={\mathtt{5}}\end{array}\right)}$$