Respuestas

2013-03-31T19:22:04+02:00

1/3 + 1/4 = 4/12 + 3/12 = 7/12 

12/12- 7/12 = 5/12 

5/12 = 20 ; 7/12 = x

x = 4

7/12=28

28+20=48 alumnos ay