39. Сократите: а) 8-11/33-4; б) 18-25/75-12; в) 6-7+7-5/49

Ответ:

а) $$rac{8 cdot 11}{33 cdot 4} = rac{8 cdot 11}{11 cdot 3 cdot 4} = rac{8}{3 cdot 4} = rac{2 cdot 4}{3 cdot 4} = rac{2}{3}$$

б) $$rac{18 cdot 25}{75 cdot 12} = rac{6 cdot 3 cdot 25}{25 cdot 3 cdot 6 cdot 2} = rac{1}{2}$$

в) $$rac{6 cdot 7 + 7 cdot 5}{49} = rac{7 cdot (6+5)}{7 cdot 7} = rac{11}{7} = 1rac{4}{7}$$