We have the following pattern
[tex]\frac{n}{8}+\frac{1}{4}[/tex]
in the first column, we have
[tex]\frac{1}{8}+\frac{1}{4}=\frac{1}{8}+\frac{2}{8}=\frac{3}{8}[/tex]
in the second column we have:
[tex]\frac{2}{8}+\frac{1}{4}=\frac{1}{4}+\frac{1}{4}=\frac{2}{4}=\frac{1}{2}[/tex]
in the third one:
[tex]\frac{3}{8}+\frac{1}{4}=\frac{3}{8}+\frac{2}{8}=\frac{5}{8}[/tex]
-> so in the 3rd column the sum is 5/8
Now, in the 4th column we have:
[tex]\frac{4}{8}+\frac{1}{4}=\frac{1}{2}+\frac{1}{4}=\frac{2}{4}+\frac{1}{4}=\frac{3}{4}[/tex]
-> thus, the addends are 1/2 + 1/4 and the sum is 3/4
