Answer by JKismyhusbandbae:
[tex]\mathrm{Add\:}3\mathrm{\:to\:both\:sides}\\15x-3+3=9x+1+3\\Simplify\\15x=9x+4\\\mathrm{Subtract\:}9x\mathrm{\:from\:both\:sides}\\15x-9x=9x+4-9x\\\mathrm{Simplify}\\6x=4\\\mathrm{Divide\:both\:sides\:by\:}6\\\frac{6x}{6}=\frac{4}{6}\\\mathrm{Simplify}\\x=\frac{2}{3}[/tex]