a) 5/6∙7/3: 5/7+ 5/9: (−5/6) + 1/5 b) −8/3−4/5∶ (−4/7) ∙5/6−9/7 c) −7/8∙ (−4/5) : (−3//4) −3/4∙5/6 d) 7/5∶8/7∙ (−4/3) :2/7∙3/4+2/3∙ (−7/8) −1/3