a) 5,23 + x = -7,24;

x = -7.24 - 5.23;

x = -12.47;

б) y - 2 5/12 = -3 7/15;

y = -3 7/15 + 2 5/12;

y = -52/15 + 29/12;

y = -208/60 + 145/60 = -63/60.