To determine the value of $t$, we'll first calculate the total amount of money John received in $50 and $20 bills, then subtract that from the $630 check to find the amount represented by the $10 bills.

1. Value of three $50 bills:

$3 \times 50 = 150 \text{ dollars}$

2. Value of eighteen $20 bills:

$18 \times 20 = 360 \text{ dollars}$

3. Total value of the $50 and $20 bills:

$150 + 360 = 510 \text{ dollars}$

4. Amount left for the $10 bills:

$630 - 510 = 120 \text{ dollars}$

5. Value of $t$ $10-dollar bills:

Since $t \times 10$ must equal $120:

$t = \frac{120}{10} = 12$

So, $t$ is 12.

Would you like more details or have any questions about this?

Here are 5 related questions:

1. What if John received four $50 bills instead of three?
2. How much money would John receive if the teller gave him twenty-five $20-dollar bills and no $50-dollar bills?
3. If John received $5 bills instead of $10 bills, how many $5 bills would he have received?
4. What would the total amount be if the check was for $750, with the same number of $50 and $20 bills?
5. If John wanted only $100 bills, how many would he receive from the $630 check?

Tip: Always break down the problem into smaller parts to handle calculations step by step, which helps avoid errors.