Приведите дроби к общему знаменатилю и сложите их:
а)1/4 + 2/3 =
б)2/7 + 2/3 =
в)2/5 + 1/4 =
г)1/2 + 1/3 =  

а) 1/4 + 2/3 = 3/12 + 8/12 = 11/12
б) 2/7 + 2/3 = 6/21 + 14/21 = 20/21
в) 2/5 + 1/4 = 8/20 + 5/20 = 13/20

г) 1/2 + 1/3 = 3/6 + 2/6 = 5/6

а) 1/4 + 2/3 = (3*1)/12 + (4*2)/12 = 3/12 +8/12 = 11/12
б) 2/7 + 2/3 = (3*2)/21 + (7*2)/21 = 6/21 + 14/21= 20/21
в) 2/5 + 1/4 = (4*2)/20 + (5*1)/20 = 8/20 + 5/20 = 13/20

г) 1/2 + 1/3 = (3*1)/6 + (2*1)/6 = 3/6 + 2/6= 5/6