The expression "the sum of 8 times $a$ and 4" can be written mathematically as:

$8a + 4$

This expression represents the sum of $8$ times the variable $a$ and $4$.

Would you like further details or have any questions?

Here are 5 related questions:

1. How would you solve the equation $8a + 4 = 0$ for $a$?
2. What happens to the expression $8a + 4$ if $a = 2$?
3. How would you factor the expression $8a + 4$?
4. Can you expand the expression $8(a + 1/2)$ and compare it to $8a + 4$?
5. How would you graph the equation $y = 8a + 4$?

Tip: When simplifying algebraic expressions, always look for common factors that can make the process easier!