Respuesta :

Answer:

B) {8.71}

Step-by-step explanation:

3. l.c.m=28

28×3/7=28×b-7/4

4×3=7(b-7)

12=7b-49

12+49=7b

61=7b

61/7=7b/7

8.71=b

b=8.71.