$$\frac{4-sin\alpha }{1-sin\alpha }-\frac{25}{4co{s}^2\alpha }+\frac{2}{1+sin\alpha }$$

$$=\frac{4-sin30°}{1-sin30°}-\frac{25}{4co{s}^{2}30°}+\frac{2}{1+sin30°}$$

$$=\frac{4-{\displaystyle \frac{1}{2}}}{1-{\displaystyle \frac{1}{2}}}-\frac{25}{4{\left({\displaystyle \frac{\sqrt{3}}{2}}\right)}^2}+\frac{2}{1+{\displaystyle \frac{1}{2}}}$$

$$=\frac{{\displaystyle \frac{8-1}{2}}}{{\displaystyle \frac{2-1}{2}}}-\frac{25}{4{\displaystyle \frac{3}{4}}}+\frac{2}{{\displaystyle \frac{2+1}{2}}}$$

$$=\frac{{\displaystyle \frac{7}{2}}}{{\displaystyle \frac{1}{2}}}-\frac{25}{3}+\frac{2}{{\displaystyle \frac{3}{2}}}$$

$$=\frac{7·2}{2·1}-\frac{25}{3}+\frac{2·2}{3}$$

$$=7-\frac{25}{3}+\frac{4}{3}$$

$$=\frac{21-25+4}{3}$$

$$=0$$