X/3+1=7/15
$ \begin{array}{l}
\frac{x}{3} \ +\ 1\ =\ \frac{7}{15}\\
\\
\\
\frac{x}{3} \ =\ \frac{7}{15} \ -\ 1\\
\\
\\
\frac{x}{3} \ =\ \frac{7\ -\ 15}{15}\\
\\
\\
\frac{x}{3} \ =\ \frac{-8}{15}\\
\\
\\
x\ =\ \frac{-8\ \times \ 3}{15}\\
\\
\mathbf{x\ =\ \frac{-24}{15}}
\end{array}$
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