Let's solve the expression $5(a + 3b)$ given that $a = 4$ and $b = -3$.

Step 1: Substitute the values of $a$ and $b$ into the expression.

$5(a + 3b) = 5(4 + 3(-3))$

Step 2: Simplify inside the parentheses.

$4 + 3(-3) = 4 - 9 = -5$

Step 3: Multiply by 5.

$5(-5) = -25$

Thus, the value of the expression is $-25$.

Would you like further explanation or any additional details?

Here are five related questions:

1. How would the expression change if $b = 3$ instead of $-3$?
2. What happens if you use a different constant outside the parentheses, like $7(a + 3b)$?
3. How would you expand the expression $5(a + 3b)$ before substituting the values of $a$ and $b$?
4. Can you solve a similar expression $4(a - 2b)$ with the same values for $a$ and $b$?
5. What is the result if $b = 0$, keeping $a = 4$ in the expression $5(a + 3b)$?

Tip: When simplifying expressions, always handle operations inside parentheses first.