10 баллов номер 1091

1091.1) 5/6 * 9/15 - 5/12 * 4/15 =[latex] frac{5}{2*3}* frac{3*3}{3*5} - frac{5}{3*4}* frac{4}{3*5}= frac{1}{2}- frac{1}{9}= frac{7}{18} [/latex]2)[latex] frac{7}{2*9}* frac{9}{2*7}+ frac{1}{3}* frac{2*3}{7}= frac{1}{4}+ frac{2}{7}= frac{15}{28} [/latex]3)[latex] frac{3*3*2}{5*4*3}+ frac{5*7}{2*7*5*5}= frac{6}{10}+ frac{1}{10}= frac{7}{10} [/latex]4)[latex] frac{15*2}{4*5}- frac{81*5}{27*25}= frac{3}{2}- frac{3}{5}= frac{9}{10} [/latex]