2.77+(-0.25)= 2.52
..................................
4 5/19+х+1 1/38=12 1/2
81/19+х+39/38=25/2
162/38+39/38+х=25/2
х=25/2-201/38
х=475/38-201/38
х=274/38=137/19=7 4/19