To find an expression for the total number of jelly beans in the customer's order, let's break it down step by step.

1. Large packets:

   • Each large packet contains $t$ jelly beans.
   • The customer orders $x$ large packets.
   • The total number of jelly beans from the large packets is $x \times t$.

2. Small packets:

   • Each small packet contains $z$ jelly beans.
   • The customer orders $y$ small packets.
   • The total number of jelly beans from the small packets is $y \times z$.

3. Loose jelly beans:

   • The customer orders $l$ loose jelly beans.

Now, to find the total number of jelly beans in the customer's order, you sum up all the jelly beans from the large packets, small packets, and loose jelly beans:

$\text{Total jelly beans} = (x \times t) + (y \times z) + l$

So, the expression for the total number of jelly beans in the customer's order is:

$\boxed{xt + yz + l}$

Would you like more details or have any questions?

Here are five related questions:

1. If $t = 10$, $z = 5$, and the customer orders 2 large packets, 3 small packets, and 7 loose jelly beans, how many total jelly beans are in the order?
2. How would the expression change if the customer also ordered an additional packet with a fixed number of jelly beans, say $k$?
3. Can this expression be used if there are multiple types of small packets, each with a different number of jelly beans?
4. What happens to the total if the number of loose jelly beans doubles?
5. How can you write the expression if the customer orders the same number of jelly beans in both large and small packets?

Tip: Always substitute values carefully when using expressions to avoid errors in calculations.