When we substitute values in math, we turn letters into real numbers that make sense.

Let’s look at this expression: $2x + 3$.

If we say $x = 5$, here’s how we can figure it out:

1. First, we find the value: $x = 5$.
2. Next, we put it in the expression: $2(5) + 3$.
3. Then, we do the math: $10 + 3 = 13$.

This shows us the number that the expression equals, which helps us understand algebra better!