А)-0.37+4.2-4.63=-0.37-4.63+4.2=-5+4.2=-08
б)-13.96+15.87+2.51=-13.96+ 18.38=18.38-13.96= 4.42
в)55/16-5/12+75/16=55/16+75/16-5/12=130/16-5/12=65/8-5/12=195/24-10/24=185/24=7целых21/24
-8.9-3.7+х=-13/6
х-12.6=-13/6
х=-13/6+126/10
х=-130/60+756/60
х=626/60
х=10целых13/30