well, let's simply see how much is 6.5% of 135, or namely the tax
[tex]\begin{array}{|c|ll} \cline{1-1} \textit{a\% of b}\\ \cline{1-1} \\ \left( \cfrac{a}{100} \right)\cdot b \\\\ \cline{1-1} \end{array}~\hspace{5em}\stackrel{\textit{6.5\% of 135}}{\left( \cfrac{6.5}{100} \right)135}\implies 8.775 \\\\[-0.35em] ~\dotfill\\\\ \stackrel{cost}{y}=\stackrel{selling~price}{x}+\stackrel{tax}{\left( \frac{6.5}{100} \right)x}~\hfill y = 135+8.775\implies y \approx 143.88[/tex]