To find the total amount of wood Frank needs for the table legs, you can multiply the number of pieces of wood by the length of each piece.
Frank needs 4 pieces of wood, and each piece is \( \frac{7}{8} \) of a foot long.
So, the calculation is:
\[ 4 \times \frac{7}{8} \]
To perform the multiplication:
\[ 4 \times \frac{7}{8} = \frac{4 \times 7}{8} = \frac{28}{8} \]
Now simplify \( \frac{28}{8} \):
\[ \frac{28}{8} = \frac{7}{2} = 3.5 \]
Thus, the total amount of wood he needs for the legs is 3.5 feet.