1) =((7-6)+(1/9 - 7/12)):19+55/10 * 2/11=(1+4/36 - 21/36):19+5= -16/36 * 1/19+5=5- 4/171=851/171=4 170/171
2) =((6-5)+(5/14-16-21)):25+36/10 * 5/9=(1+15/42-32/42):25+4= -17/42 * 1/25+4= 4 - 383/1050= 3817/1050=3 667/1050
3) = ((8-7)+(5/12-17/18)):17+72/10 * 5/12=(1+ 15/36=34/36):17+6= -19/36 * 1/17+6=6 - 287/612=3385/612==5 325/612