Respuesta :

7/8+9/10=71/40=1 31/40
1/4+2/3=11/12
1/2+1/4 is different from 1/2+1/3 because 
1/2+1/4= 2/4+1/4=  5/1 =1  1/4
1/2+1/3=3/6+2/6=5/6