Subtract seven square root 5-4 square root five what is the difference?

To subtract \( 4\sqrt{5} \) from \( 7\sqrt{5} \), you can combine the two terms:

\[
7\sqrt{5} - 4\sqrt{5} = (7 - 4)\sqrt{5} = 3\sqrt{5}
\]

So, the difference is \( 3\sqrt{5} \).