Помогите решить примеры: 19/42-5/63 (7/10+3/5) — (1/6+2/3) 2/3- (1/20+2/9) -5/181/3+1/4+1/5+1/6+1/7

19/42-5/63=(57-10) 126=47/126 (7/10+3/5) — (1/6+2/3)=7/157/10+3/5=(7+6) /10=13/101/6+2/3=(1+4) /6=5/613/10-5/6=(39-25) /30=14/30=7/152/3- (1/20+2/9) -5/18=7/601/20+2/9=(9+40) /180=49/1802/3-49/180=(120-49) /180=71/18071/180-5/18=(71-50) /180=21/180=7/601/3+1/4+1/5+1/6+1/7=(140+105+84+70+60) /420=459/420=1 39/420