It looks like there is a minor issue with the notation in your expression. Specifically, you wrote $5_5$, which isn’t standard. Did you mean to write something like $5 \times 5$, or did you mean another mathematical operation or concept?

If you're aiming to simplify the expression $3x + 7 - 5 \times 5$, we can proceed like this:

1. First, calculate $5 \times 5 = 25$.
2. Substitute into the equation: $3x + 7 - 25$.
3. Simplify further: $3x + (7 - 25) = 3x - 18$.

So, the expression simplifies to: $3x - 18$

If you meant something different, let me know, and I’ll correct the interpretation.

Would you like further clarification or help with a different problem? Here are 5 related questions you can explore:

1. How do you solve equations that involve terms like $3x - 18 = 0$?
2. What happens when you distribute in an expression like $3(x + 5)$?
3. How do you handle negative signs in algebraic expressions?
4. What are the steps to factor an expression like $3x - 18$?
5. What is the significance of simplifying expressions in algebra?

Tip: When simplifying expressions, always perform operations inside parentheses first, and then follow the order of operations (PEMDAS).