a , b , c , d ???????????????????

Answer:
First, add the two mixed numbers together.
[tex]1 + 2 = 3[/tex]
[tex]4/7 + 3/14 = 11/14[/tex]
Combine the equation and number.
[tex]3 + 11/14 = 3 \frac{11}{14}[/tex]
[tex]3\frac{11}{14} + 1/2 =[/tex] 4 2/7
Therefore, the answer is 1/2