The expression shown in the image is:

$\sqrt{25} - \sqrt{49}$

We can now simplify this:

$\sqrt{25} = 5$ $\sqrt{49} = 7$

Thus, the expression becomes:

$5 - 7 = -2$

The final result is $-2$.

Would you like more details or have any questions?

Here are five questions that expand on this topic:

1. What is the general process for simplifying square roots?
2. Can square roots of non-perfect squares be simplified in a similar way?
3. How can you use square roots in solving quadratic equations?
4. What is the difference between simplifying a square root and solving a square root equation?
5. Can the negative of a square root exist in real numbers?

Tip: When simplifying square roots, always check if the number under the square root is a perfect square to make the process easier.