1) -2 1/5 +5/2 = - 1 6/5 + 5/23 = -1 (6*23 -5*5)/(5*23) = -1 113/115 или -228/115 ;
по другому :-(11/5 -5/23) = -(11*23 -5*5)/(5*23) = - 228/115 .
2) 9/3 -1 20/51 = 2 51/51 -1 20/51= 1 31/51 = 82/51;
3) x= 82/51 * (- 228/115) ;
x = - (82*228)/ (51*115) = - 18696/ 5865. [-3 1001/5865 ] .