To calculate the total number of computers in each case, we simply add the number of notebook computers and the number of desktop computers.

Case 1: 15 notebooks and 11 desktop computers

$\text{Total Computers} = 15 + 11 = 26$

Answer for Case 1: 26 computers.

Case 2: $n$ notebooks and $d$ desktop computers

$\text{Total Computers} = n + d$

Answer for Case 2: $n + d$ computers.

Would you like further clarification or assistance with similar problems? Here are five related questions to explore:

1. How much would it cost to buy 15 notebooks and 11 desktops at the given prices?
2. What is the total cost if you buy $n$ notebooks and $d$ desktops?
3. If the budget is $5,000, how many notebooks can be purchased if only notebooks are bought?
4. What is the ratio of the cost of a notebook to a desktop computer?
5. How much would it cost if the school decides to buy an equal number of notebooks and desktops?

Tip: Break down problems into smaller steps to ensure clarity in calculations.