Respuesta :

Answer:

required sum=a+4b

Step-by-step explanation:

given 3a-4b,7b+c,c-3a and a+b-2c

required sum=3a-4b+7b+c+c-3a+a+b-2c

                     =3a-3a+a-4b+7b+b+c+c-2c

                     =a+4b

hence required sum=a+4b    answer