The problem shown in the image asks to find the value of:

$10\sqrt{5} - 4\sqrt{5} - 7\sqrt{5}$

Solution:

We can simplify this expression by factoring out the common term $\sqrt{5}$:

$(10 - 4 - 7) \sqrt{5}$

First, perform the subtraction inside the parentheses:

$10 - 4 - 7 = -1$

Thus, the expression simplifies to:

$-1\sqrt{5} = -\sqrt{5}$

So, the correct answer is A. $-\sqrt{5}$.

Would you like more details or further explanations?

Here are 5 related questions for practice:

1. What is the value of $3\sqrt{3} + 5\sqrt{3} - 8\sqrt{3}$?
2. How would you simplify $2\sqrt{2} + 3\sqrt{2} - \sqrt{2}$?
3. Solve $9\sqrt{7} - 2\sqrt{7} + 6\sqrt{7}$.
4. What is the result of $4\sqrt{11} - 5\sqrt{11}$?
5. Simplify $12\sqrt{6} - 9\sqrt{6} + 5\sqrt{6}$.

Tip: When dealing with terms involving square roots, always look for common factors to simplify.