79/80-(3/16+39/80)=5/163/16+39/80=(3*5+39)/80=54/8079/80-54/80=(79-54)/80=25/80=5/162/45+(41/45-7/9)=8/4541/45-7/9=(41-7*5)/45=6/452/45+6/45=(2+6)/45=8/457/15 -(2/15+1/5)= 2/15 (здесь знак пропущен?! я поставила -)2/15+1/5=(2+1*3)/15=5/157/15-5/15=(7-5)/15=2/153/16+(15/16-5/8)=15/16-5/8=(15-2*5)/16=5/163/16+5/16=(3+5)/16=8/16=1/2