When building the query for exercise 3:

"How many orders did each customer make? Use the items_ordered table. Select the customerid, number of orders they made, and the sum of their orders."

My answers look significantly different from the results obtained by using the answer provided. Look at the third column, and compare the two results. When I read the source table it appears that some of the orders have multiple items associated with them. This should affect the sum that is requested. If all one does is sum the column, none of the multiple items are included in the total. The "answers" query structure is as follows:

SELECT customerid, count(customerid), sum(price)
FROM items_ordered
GROUP BY customerid;

This yields a result of:
10101 6 320.75
10298 5 118.88
10299 2 1288
10315 1 8
10330 3 72.75
10339 1 4.5
10410 2 281.72
10413 1 32
10438 3 95.24
10439 2 113.5
10449 6 930.79

I feel that you should be including the multiples by the following query:

SELECT customerid, count(customerid), sum(quantity*price)
FROM items_ordered
GROUP BY customerid;

which then results in:
10101 6 813.95
10298 5 147.88
10299 2 1288
10315 1 8
10330 3 156.75
10339 1 4.5
10410 2 281.72
10413 1 128
10438 3 95.24
10439 2 139
10449 6 970.79

Is my understanding of the question, or the presented data faulty? Or should we use the multiplier to get correct results?
I'm only asking this because I'm a real neophyte at this SQL query thing - that's why I'm taking the tutorial lessons - and I'd like to be sure I'm reading this correctly. I did check my results and they are consistent with my logic.