(c-5d)-(-d+5c)= (-2.8+13)-(5.6+2.8)+(2.8-13)=

(c-5d)-(-d+5c)=c-5d+d-5c=-4c-4d= -4(c+d) (-2.8+13)-(5.6+2.8)+(2.8-13)=-2.8+13-5.6-2.8+2.8-13=-2.8-5.6= -8.4