[tex]\displaystyle\bf\\\frac{1,5Sin\alpha -Cos\alpha }{Cos\alpha +2Sin\alpha } =\frac{\dfrac{1,5Sin\alpha }{Sin\alpha } -\dfrac{Cos\alpha }{Sin\alpha } }{\dfrac{Cos\alpha }{Sin\alpha } +\dfrac{2Sin\alpha }{Sin\alpha } } =\frac{1,5-Ctg\alpha }{Ctg\alpha +2} \\\\\\Ctg\alpha =\frac{1}{2} =0,5\\\\\\\frac{1,5-Ctg\alpha }{Ctg\alpha +2} =\frac{1,5-0,5}{0,5+2} =\frac{1}{2,5} =0,4[/tex]