Решение:
а) $\frac{23 * 35 + 38 * 35}{17 * 61 + 18 * 61} = \frac{35 * (23 + 38)}{61 * (17 + 18)} = \frac{\overset{1}{\cancel{35}} * \overset{1}{\cancel{61}}}{\underset{1}{\cancel{61}} * \underset{1}{\cancel{35}}} = \frac{1 * 1}{1 * 1} = 1$;
б) $\frac{49 * 99 + 28 * 99}{12 * 154 + 21 * 154} = \frac{99 * (49 + 28)}{154 * (12 + 21)} = \frac{\overset{3}{\cancel{99}} * \overset{1}{\cancel{76}}}{\underset{2}{\cancel{154}} * \underset{1}{\cancel{33}}} = \frac{3 * 1}{2 * 1} = \frac{3}{2} = 1\frac{1}{2}$;
в) $\frac{75 * 27 + 75 * 37}{37 * 48 - 12 * 48} = \frac{75 * (27 + 37)}{48 * (37 - 12)} = \frac{\overset{3}{\cancel{75}} * \overset{8}{\cancel{64}}}{\underset{6}{\cancel{48}} * \underset{1}{\cancel{25}}} = \frac{3 * 8}{6 * 1} = \frac{24}{6} = 4$;
г) $\frac{679 * 846 + 679 * 54}{679 * 846 - 679 * 46} = \frac{679 * (846 + 54)}{679 * (846 - 46)} = \frac{\overset{1}{\cancel{679}} * \overset{9}{\cancel{900}}}{\underset{1}{\cancel{679}} * \underset{8}{\cancel{800}}} = \frac{1 * 9}{1 * 8} = \frac{9}{8} = 1\frac{1}{8}$.
Ответ:
а) $1$;
б) $1\frac{1}{2}$;
в) $4$;
г) $1\frac{1}{8}$.