[tex] \huge \purple{\tt{Answer:}} [/tex]
Let the unknown number be x .
[tex] \Large{\underline{\sf{According~to~question}}} [/tex]
[tex] \sf {2x+15=9} \\\\\ \implies \sf{2x=9-15} \\\\\ \implies \sf {2x=-6} [/tex]
[tex] \implies {\sf {x ={ \dfrac{ - 6}{2}}}} \\\\\ \implies \sf{x=-3} [/tex]
