А) 7/65+2/15+6/65= 21+26+18/195=65/195=13/39 б) 19/63-(10/63+1/14)= 19/63-10/63-1/14=19-10-4,5/63=4,5/63=1/14 в) (18/55+2/15)-7/55=18/55+2/15-7/55=54+22-21/165=55/165=11/33